Lesson 6: Carbohydrates

Table of Contents


In the last two lessons I discussed protein and fat, the benefits they may or may not confer for dieting and weight loss, the recommended amounts and types for health purposes, and other relevant considerations. In this lesson I will do the same for carbohydrates while also considering the topics of added sugar, artificial sweeteners, and the glycemic index and load. I will discuss sources of carbohydrates as well as gluten in Lesson 10 when I talk about grains as a food group.


Specific considerations for exercise and weight management

In general no meaningful differences are seen in weight management outcomes when comparing low carbohydrate vs. low fat diets if calories are matched.(Blaak, 2021; Yang, 2021) This seems to also extend to weight maintenance after weight loss.(van Baak, 2021)

Carbohydrate intake can aid glycogen replenishment to provide energy for workouts.(Murray, 2018) For people eating at maintenance calories who are not doing extended aerobic training sessions this is generally not a significant concern unless you train twice within an 8-hour period. However, when eating at a caloric deficit it can be harder to replenish glycogen levels effectively to fuel a workout without sufficient carbohydrate intake.

Some people subjectively find consuming carbohydrates prior to a workout allows them to perform their workout with higher intensity. In the protein lesson I discussed that the timing of protein intake in relation to a workout is not very significant. For carbohydrate intake, though, it can be significant. As different people respond differently, it can take trial and error to determine the best source, quantity, and timing of pre-workout carbohydrates to best fuel your workout sessions.

Tip: A “fundamental principal” of a healthy lifestyle including exercise sessions is to make the exercise sessions the best they can be. Being able to train with more focus and intensity will yield better results. For this reason, I recommend trialing a variety of different food/drink items prior to a workout (and potentially during a workout) to determine what allows you to train to the best of your ability. I discuss eating in relation to exercise in more detail in Lesson 15 of the general exercise course. Some considerations:

  • Consuming too much food/drink too close to the workout can lead to gastrointestinal discomfort
  • Eating carbohydrates alone will lead to faster digestion than adding a source of protein or fat, which may or may not be helpful
  • Some people do best eating a meal several hours prior to a workout and a small snack shortly before a workout
  • Some people find they train best when they are fasting first thing in the morning
  • If training for >60 minutes it can be helpful to consume a source of carbohydrates during the workout (ie, a sports drink)

This largely comes down to personal preference and experimentation. Try different things and determine what works best for you.

Note: There are people who train while on a ketogenic diet, meaning very little carbohydrate intake, and this has been studied heavily. It is generally shown this can lead to effective cardiovascular adaptations without a negative impact on performance.(McSwiney, 2019) A caveat though is that this is only seen after being “keto-adapted”, meaning one must be on a ketogenic diet for at least several weeks prior to it no longer being detrimental.(Sherrier, 2019) For unclear reasons it seems more difficult to build new lean body mass in response to resistance training while on a ketogenic diet(Vargas, 2018) and it seems difficult to maintain lean body mass while losing weight.(Ashtary-Larky, 2021) I will discuss ketogenic diets further in Lesson 13.

Minimum carbohydrate intake for health purposes

The recommended dietary allowance (“RDA”) for carbohydrate intake at all ages >1 year old is 130 grams of carbohydrate daily. The acceptable macronutrient distribution range (“AMDR”) is 45-65% of your total daily calories.

Note: The RDA was set with the thought that 100 grams of carbohydrate intake daily will provide enough glucose for brain function for ~50% of people; adding two standard deviations to this yields 130 grams. However, we know that many people function well on fewer carbohydrates than this. Those on a ketogenic diet (at times prescribed for medical purposes) generally eat considerably fewer than 50 grams of carbohydrates daily.

The AMDR was set with an upper limit based on data that low fat, high carbohydrates worsen blood cholesterol levels and thus increase the risk of coronary heart disease. The lower limit comes from the thought that low carb, high fat diets will lead to people overeating and increase their risk of developing obesity.

However, the data used to generate these recommendations are several decades old, and it is now more clear that the source of nutrients rather than just the quantities play a large role in dictating health outcomes. Therefore, while these recommendations exist and are frequently cited, in my opinion they deserve to be updated.

In light of the above, I do not believe there is a true minimum amount of carbohydrates needed daily; there are technically no essential carbohydrates that the body requires and energy can be generated from fat and protein. However, for health purpose, there are several sources of carbohydrates with health benefits, such as fruits(Fardet, 2019), vegetables(Wallace, 2019), and whole grains(Jones, 2020). A healthy diet including these food sources will require some level of carbohydrate intake. These food groups, and thus sources of carbohydrates, are discussed more fully in Lesson 10.

Maximum carbohydrate intake for health purposes

There are some common concerns of high-carbohydrate diets, including that they lead to weight gain, diabetes, or high cholesterol. However, there are several studies indicating these concerns are not valid, particularly when the source of carbohydrates are fruits, vegetables, and fiber-rich grains.(Sartorius, 2018; Sylvetsky, 2017) In fact, there is a specific diet, referred to as the Ma-Pi 2 diet, that has shown good outcomes in short term trials on cardiovascular risk factors and glycemic control in adults with type 2 diabetes; in these trials on average 70% of calories came from carbohydrates.(Porrata-Maury, 2014)

Note: I do not actually recommend the Ma-Pi 2 diet as it is difficult to follow, restrictive, and expensive, but I wanted to include it as an example of a high-carbohydrate diet that can yield good outcomes, at least in the short term in adults with type 2 diabetes. In general, low-carbohydrate diets have been found to be helpful in individuals with type 2 diabetes, at least for up to 6 months duration, but it’s unclear if this is due to the lower carbohydrate intake or due to the greater calorie restriction that this type of diet typically induces.(Jayedi, 2022)

Therefore, the total quantity of carbohydrates one consumes seems less relevant, at least when the food sources are fruits, vegetables, and fiber-rich grains, though there may be some concern of cardiovascular disease with >60% of energy intake coming from carbohydrates in Asian populations.(Jo, 2023) Overall, I do not believe there is a true maximum amount of carbohydrates above which one will be at risk of harm, assuming this does not lead to excessive caloric consumption and the carbohydrate intake is coming from more nutritious sources.


Consideration of added sugar

The general recommendation for added sugar intake is to limit this to <10% of your daily calories. However, this is largely to help ensure there is room for other healthy nutrients while still keeping total calories at a reasonable level as explained in the United States Department of Agriculture and Health and Human Services (USDA-HHS) response to the Dietary Guidelines Advisory Committee’s Report that was used to develop the 2020-2025 Dietary Guidelines for Americans:

"However, after careful consideration of the totality of evidence presented by the Committee, the Dietary Guidelines for Americans, 2020-2025 retains the recommendation to limit intakes of added sugars to less than 10 percent of calories per day in the 2015-2020 Dietary Guidelines. The introduction of this quantitative recommendation was based on significant scientific agreement from data analysis, systematic reviews, and food pattern modeling, and largely, the science has not changed. According to food pattern modeling, the amount of calories available from added sugars varies depending on caloric needs...For those people who need higher calorie intakes per day, an upper limit of 10 percent of calories from added sugars may be consumed while still meeting food group recommendations in nutrient-dense forms.

There are several lines of evidence that added sugar intake >10% of your total daily calories can be safe in individuals who are keeping total caloric intake at a level to obtain/maintain a healthy body weight and composition while exercising regularly.(Rippe, 2015) This extends to considerations of blood pressure, lipids, and glycemic control in some scenarios, though less likely with sugar-sweetened beverages.(Prinz, 2019a; Perrar, 2019; Prinz 2019b) A 2022 review highlights that added sugar in sugar-sweetened beverages likely does contribute to health risks, but this may not extend to added sugar in solid foods.(Yan, 2022) On the other hand, there is a possible increased risk of some cancer types with added sugar intake, although this evidence is epidemiological in nature.(Makarem, 2018) Fructose in particular may be the most harmful when consumed in excess, and as it is frequently found in sugar-sweetened beverages (which are associated with worse health outcomes) it makes sense to minimize sugar-sweetened beverage consumption to keep added sugar at <10% of your daily calories.(Blaak, 2021; Wang, 2022; Chiavaroli, 2023)

Overall, keeping added sugar at <10% of your daily calories is a reasonable goal, though occasionally going over this is unlikely to pose significant health risks.

Note: To be clear, as recently reviewed, the potential safety of going above 10% daily calories with added sugar depends on this not leading to elevated caloric intake and undesired weight gain.(Veit, 2022) If tracking calories this can be well-controlled but if not tracking calories it can be rather difficult to eat substantial amounts of food with added sugar and not start to gain weight. This is in part due to processed foods with added sugar being less satiating than unprocessed whole foods.(Hall, 2019)

Artificial sweeteners as a substitute for added sugar?

While not technically carbohydrates, artificial sweeteners are frequently used as a substitute for added sugar and thus they are worth discussing here. This is a controversial topic; at this point the majority of the literature suggests that artificial sweeteners can be used safely in moderation. For an overview of the research on this topic, click below.

Artificial sweeteners, also referred to as low-calorie sweeteners (“LCS”) and non-nutritive sweeteners (“NNS”), pose yet another controversial topic in the literature, primarily regarding their impact on body weight as well as glucose and insulin control. I will discuss some of the more recent literature here.

Some select 2018 references:

  • In a 12-week trial, 100 healthy adults with body mass index (“BMI”) 18-25 and low habitual consumption of LCS were split into 3 groups (control, 350 mg of aspartame daily (equivalent to ~1 can of low calorie soda), and 1,050 mg of aspartame daily).(Higgins, 2018) An oral glucose tolerance test (OGTT) conducted before and after the 12-week period showed no differences in glucose or insulin response, and there were additionally no differences in weight or appetite.
  • In a 14-day trial, 30 healthy adults with normal BMI and low habitual consumption of LCS were given ~45% of the acceptable daily intake for sucralose divided into 3 doses daily.(Romo-Romo, 2018) With an OGTT blood glucose response did not change but insulin sensitivity decreased 17.7% after the trial (a control group had a decrease of 2.8%).
  • A review highlighted some of the harmful effects of LCS consumption on weight control and metabolic diseases seen in epidemiological studies and contrasted this with the neutral or even beneficial effects seen in controlled trials, indicating longer, well-controlled intervention studies are needed.(Sylvetsky, 2018)

Some select 2019 references:

  • A policy statement by the American Academy of Pediatrics regarding LCS consumption in children and adolescents also acknowledged the literature is conflicting, there may be reverse causality explaining some of the negative associations seen in the observational literature, and trials indicate artificial sweeteners can have positive benefits for weight management.(Baker-Smith, 2019)
  • In a 12-week trial, 123 healthy adults with BMI 25-40 who were not habitual consumers of LCS at baseline were randomly assigned into 5 groups.(Higgins, 2019) One group was given a beverage to drink daily consisting of sucrose (sugar); the volume was based on the individual’s body weight and the beverages had either 400, 480, or 560 kcals. The other four groups were given beverages without sucrose that had sweetness matched with one of four tested LCS (saccharin, aspartame, rebA, sucralose). There was more body weight gain with sucrose (1.85 kg) than with any of the artificial sweeteners (1.18 kg for saccharin, no significant gain in the other groups). There were no differences between fasting glucose, fasting insulin, or glucose & insulin responses to an OGTT before and after the intervention.

Some select 2020 references:

  • A systematic review & meta-analysis (“SR/MA”) of human intervention studies investigating the acute effect of LCS consumption on postprandial glucose & insulin responses found they collectively have no impact.(Greylink, 2020) A commentary highlighted some of the methodological issues that have plagued the observational and intervention studies previously and showed there are several planned & ongoing trials as well as SR/MAs which will address some of this ambiguity.(Khan, 2020)
  • A review specifically evaluated the impact of aspartame & sucralose (two of the most commonly used LCS) on glucose responses and gut hormones (these are implicated in appetite control).(Ahmad, 2020) The authors found most studies show no impact of the LCS but a small handful show positive or negative effects. The authors highlight that more research with better designed protocols is needed.
  • A SR/MA of randomized controlled trials of at least 4-weeks duration found that LCS consumption (aspartame was primarily included in the trials) had a beneficial effect on weight change in individuals with an elevated BMI when consuming non-calorie restricted diets.(Laviada-Molina, 2020) This only extended to comparisons with sucrose, there was no benefit when compared to water or a placebo.
  • In a 2-week trial, 45 adults without obesity and with low habitual consumption of LCS were split into 3 groups, each consuming a drink 7 times in a 2-week time span.(Dalenberg, 2020) The drinks either contained 120 kcal of sucrose, the LCS sucralose (in an amount to match sweetness with the sucrose beverage), or a combination of maltodextrin (a non-sweet carbohydrate) and sucralose (also to match sweetness of the sucrose beverage. They subsequently added a control group with maltodextrin only. Brain scans as well as an OGTT and other testing were done before and after the 2-week intervention. They found worse insulin metrics with the maltodextrin + sucralose drink than with either sucrose, sucralose, or maltodextrin alone.
    • The authors interpret this to suggest that consuming sucralose without a source of carbohydrate may not be harmful but consuming sucralose with carbohydrate may worsen insulin sensitivity.
    • However, a reanalysis of their data by separate authors employing more appropriate data analysis methods found there was actually no difference between maltodextrin + sucralose vs. maltodextrin alone.(Khan, 2021)
    • Thus, this study does not seem to provide evidence of concern regarding the impact of carbohydrates + LCS given together. Of note, even if there is legitimate concern from this study, given the small sample size and short duration this would need to be replicated on a larger scale for a greater length of time.
  • A review of SRs found lots of contradictory or null findings in the literature regarding the impact of LCS on anthropometric outcomes, cardiometabolic parameters, type 2 diabetes, cancer, and compensatory energy intake.(Andrade, 2020)

Some select 2021 references:

  • A SR/MA of intervention studies of at least 1-week duration examined LCS vs sugar, LCS vs water or nothing, and LCS vs placebo.(Rogers, 2021) Overall there was a benefit for body weight control and energy intake in the LCS vs sugar comparison group with no difference in adverse events. No consistent effects were seen in the other two comparison groups.
  • A SR/MA evaluated 34 articles of prospective cohorts regarding the associations between both sugar-sweetened beverages (SSBs) and artificially-sweetened beverages (ASBs) with type 2 diabetes, cardiovascular disease, and all-cause mortality.(Meng, 2021) There was more consistent evidence for an increased risk with the SSBs (risk of each outcome increased 27%, 9%, and 10%, respectively, with 1 additional drink daily, though the risk of all-cause mortality was not statistically significant).  With 1 additional drink of ASBs daily the risk increased 13%, 8%, and 7%, respectively, though the association with type 2 diabetes and cardiovascular disease was less evident after adjusting for confounding variables and the risk with all-cause mortality was not statistically significant. Of note, there was a statistically significant increased risk of all-cause mortality when comparing high vs low intakes for both SSBs and ASBs intake (14% and 15% increased risk, respectively).
    • Thus, from the observational literature it appears that ASBs are less harmful than SSBs, and while they may impose some level of risk this is minimized when adjusting for confounding variables. It’s possible there is unmeasured confounding that explains the remainder of the risk.

Some select 2022 references:

  • A 2022 review noted that there is an inverse correlation between BMI and sweet taste sensitivity in people with overweight or obesity and while there are still unknowns regarding the impact of artificial sweeteners on insulin responses, artificial sweeteners do not seem to contribute to compensatory energy intake or a decrease in satiety.(Wilk, 2022) There also does not seem to be an increase in preference for sweet foods after frequent exposure to sweet stimuli. Thus, there may be a psychological benefit when consuming artificial sweeteners to help satisfy your appetite for sweet taste and contribute to the reduction or elimination of snacking on high-energy foods.
  • A 2022 SR/MA including 8 cohort studies found 1 artificially sweetened drink daily was not associated with an increased risk of cardiovascular mortality, but consuming 2 or more of these drinks daily was associated with a 33% increased risk.(Bhagavathula, 2022)
  • A 2022 SR/MA comparing artificial sweeteners (mostly aspartame) to sugar-sweetened beverages found that using artificial sweeteners led to small decreases in body weight, BMI, and bodyfat %, with no evidence of long-term harm (median duration of the trials was 12 weeks though 2 trials went a full year).(McGlynn, 2022)
  • A 2022 SR of human randomized controlled trials evaluating a blend of aspartate and acesulfame-K included 8 studies and found that in general their utilized led to a ~200 kcal decrease in meal intake with no subsequent increase in appetite or change in blood glucose levels.(Mehat, 2022)
  • A 2022 randomized controlled trial for 4 weeks provided either saccharin, sucralose, aspartame + acesulfame-K, or a control to people who at baseline did not consume these more than once a week.(Orku, 2022) This resulted in no difference for glucose or insulin responses to an oral glucose tolerance test, body weight, waist circumference, or energy intake levels.
  • A 2022 randomized controlled trial tested supplements of aspartame, saccharin, sucralose, and stevia against controls of either glucose or nothing.(Suez, 2022) With 2 weeks of daily consumption in people who previously were not consuming them more than once a week they found:
    • Saccharin and sucralose increased the overall glycemic response while also changing the gut microbiome composition
    • All 4 artificial sweeteners changed the gut microbiome function
    • When performing a fecal microbiome transplant from the top and bottom responders of each group into rodents, all 4 artificial sweetener top responder samples let to higher glycemic responses in over half of the rodents and for saccharin all 3 of the bottom responders did as well
    • The amount of each artificial sweetener used per day was 240 mg of aspartame (most diet sodas have ~50-125 mg), 180 mg of saccharin (1 packet of Sweet n’ Low had ~36 mg), 102 mg of sucralose (1 packet of Splenda has 12 mg), and 180 mg of stevia (amounts vary per product)

Some select 2023 references:

  • A 2023 SR/MA included 25 reports of 36 acute feeding trials examining the impact of a single exposure to artificial sweeteners on various measures of glucose control and hunger/satiety hormones when consumed with or without calories, finding in general no impact of the artificial sweeteners in people regardless if they were generally healthy, had obesity, or had type 2 diabetes.(Zhang, 2023)
  • A study that got a lot of press found erythritol (an artificial sweetener that is naturally found in small amounts in some fruits and vegetables) was found in higher levels in people with worse health outcomes in two separate cohorts and that experimentally this essentially activated platelets and may thus contribute to clot formation in the bloodstream.(Witkowski, 2023) However, the cohort analyses did not consider dietary intake of erythritol, and it is possible that underlying disease contributed to higher blood levels. The other analyses were mostly in vitro, so their relevance for human physiology is unclear. More research should be done on this, but the study itself does not convince me that erythritol intake is harmful.
  • The WHO recently released a guideline suggesting that non-sugar sweeteners not be used for weight control purposes, but this critique of the guideline points out that the WHO guideline disregarded much of the randomized controlled trial evidence that does show a benefit in favor of the prospective cohort studies that are known to have inherent biases.(Khan, 2023)
  • A randomized controlled trial with a 12 week weight loss intervention phase and then a 40 week weight loss maintenance phase found that drinking non-nutritive sweetened beverages instead of water led to slightly greater weight loss after 1 year (-7.5 kg vs -6.1 kg), though the authors acknowledge this is not clinically significant.(Harrold, 2023)
  • A 2023 SR/MA including 28 RCTs found that non-nutritive sweeteners led to slightly greater weight loss (~1 kg change), though is is unlikely to be clinically significant.(Movahedian, 2023)
  • A 2023 SR/MAincluding 6 RCTs of ~6+ months duration found that replacing sugar-sweetened beverages with artifically-sweetened beverages or water led to a BMI decrease of ~0.3, coming to ~0.5 kg loss of body weight in children and ~1 kg loss of body weight in adults.(Tobiassen, 2023)
  • A 2023 opinion piece argues the current research is inadequate and while non-sugar sweeteners may be a tool for weight management and glycemic control in some cases, widespread replacement of added sugars with non-sugar sweeteners may have unintended consequences, especially in some subgroups.(Hedrick, 2023)


Most of the better-done research (from a methodology perspective) thus far does not observe a negative impact of LCS on body weight control or glucose and insulin levels in the body, though the most recent trial listed above did find an impact on glycemic response. However, it is difficult to draw concrete solutions due to the lack of long-term studies, potential differences between the different LCS types, and individual variability that may be at play (ie, people with different gut microbiomes may metabolize the LCS differently).

Overall, at this point in time the majority of the evidence indicates LCS consumption in moderation is safe. If using products with LCS in moderation in lieu of actual sugar aids you in sticking to an overall healthy eating plan and caloric goal then I believe this is a reasonable strategy.

Consideration of the glycemic index and glycemic load

While the body can perhaps handle increased amounts of added sugar when keeping total calories in a healthy range, another consideration is if the added sugar is consumed all at once in a rapidly digesting form (ie, a sugar-sweetened beverage) or spread out in meals that slow down its digestion. This gets into the notion of glycemic index and glycemic load:

  • Glycemic index: this is defined as the area under the curve for blood glucose response over a 2-hour period after consuming a 50 gram carbohydrate portion of both a test food and a standard food (50 grams of glucose or a 50 gram carbohydrate portion of white bread) and expressing the data as a percentage of the test food relative to the standard food.
  • Glycemic load: this takes portion size into account; the glycemic index for a food is multiplied by the quantity of carbohydrates and divided by 100.

There are several considerations here:

  • First, when calculating glycemic index values there is both interindividual variability (testing the same food item on different people) and intraindividual variability (replicating the test in the same individual), with one study showing coefficients of variation of 17.8% (interindividual) and 42.8% (intraindividual) when testing white bread in triplicate relative to glucose.(Vega-López, 2007)
  • Second, while the glycemic index technically should be tested in the morning after an overnight fast, when eating throughout the day prior meals can impact and hence alter glycemic responses of the current meal being consumed.(Ando, 2018)
  • Third, based on other real world conditions (as opposed to lab-testing conditions) and interindividual variability, specific meals may generate improved glycemic responses in some individuals while the same meals may generate worsened glycemic responses in others.(Zeevi, 2015)

For these reasons, it is not very surprising that the totality of evidence does not indicate significant health implications of the glycemic index or glycemic load, with large systematic reviews and meta-analyses indicating at most a mild impact on body weight, diabetes, cardiovascular disease, cancer, or all-cause mortality.(Vega-López, 2018; Turati, 2019; Reynolds, 2019; Gaesser, 2021)

A 2020 umbrella review of meta-analyses of prospective cohort studies found moderate quality evidence of an association between glycemic index and(Jayedi, 2020):

  • gallbladder disease (relative risk 1.26, 2 studies)
  • bladder cancer (relative risk 1.26, 2 studies)
  • type 2 diabetes (relative risk 1.18, 15 studies)
  • coronary heart disease (relative risk 1.14, 10 studies)
  • colorectal cancer (relative risk 1.12, 12 studies)
  • breast cancer (relative risk 1.06, 11 studies)

There was no increased risk of cardiovascular mortality or all-cause mortality. For glycemic load, there was moderate quality evidence of an association with:

  • gallbladder disease (relative risk 1.41, 2 studies)
  • stroke (relative risk 1.21, 7 studies)
  • type 2 diabetes (relative risk 1.11, 14 studies)

Again, there was no increased risk of cardiovascular mortality or all-cause mortality. Thus, a diet with a higher glycemic index is associated with a small risk of increased health consequences; mechanistically the biggest concern would be type 2 diabetes and it seems the risk of this when comparing high vs low glycemic index and load is only increased by <20%.

As glycemic index can reflect many other aspects of the diet (ie, fruits/vegetables/whole grains will generally have a lower glycemic index than sources of added sugar and refined grains), it is more logical to me that it is the underlying food groups (discussed in Lessons 10 and 11) and not the glycemic index per se that would have a significant health impact. I expect the glycemic index and load to be even less relevant for individuals consuming an appropriate amount of calories to attain or maintain a healthy body composition while exercising regularly.

Having said all of that, for people with significant insulin resistance or diabetes mellitus it will make more sense to consume less of the high glycemic index/load foods, particularly in isolation, as these individuals are more prone to developing much more significant elevations in their blood glucose levels. Additionally, a recent trial found that individuals who experience a larger decrease in their blood glucose level 2-3 hours after consuming a meal experience greater levels of hunger and subsequently consume more calories, and there was some evidence that meals that increase blood glucose to the highest degree subsequently led to a greater decrease in glucose.(Wyatt, 2021) While this will likely not affect everyone to the same degree, certain individuals may find that consuming high glycemic index/load foods in isolation will lead to a relative increase in their hunger levels.

Note: For individuals who are interested in looking up the glycemic index of specific foods, an updated table of values was published in 2021 and can be accessed by clicking here.(Atkinson, 2021)


Overall, much of dietary carbohydrate intake comes down to personal preference. Some people feel better and perform better with higher carbohydrate diets while some people prefer lower carbohydrate diets. Indeed, the literature as a whole does not generally suggest a preference for low-carb/high-fat vs high-carb/low-fat with regards to weight management.(Seid, 2019) Trial and error helps to determine what works best for any given individual, particularly with regards to pre-workout nutrition.

Fruits, vegetables, and whole grains with fiber all have several beneficial health properties and these sources of carbohydrates should be prioritized if sticking to lower carbohydrate intakes. If consuming higher intakes, limiting added sugar to <10% of total daily calories is the safest option, though less worrisome if one maintains a healthy body weight and composition and exercises regularly. Sugar-sweetened beverages should in particular be avoided, especially when consumed in isolation.

As I have now discussed the three primary macronutrients, in the next two lessons I will discuss fiber and alcohol.

Click here to proceed to Lesson 7


  1. Ahmad SY, Friel JK, Mackay DS. Effect of sucralose and aspartame on glucose metabolism and gut hormones. Nutr Rev. 2020 Sep 1;78(9):725-746. doi: 10.1093/nutrit/nuz099. PMID: 32065635.
  2. Ando T, Nakae S, Usui C, et al. Effect of diurnal variations in the carbohydrate and fat composition of meals on postprandial glycemic
    response in healthy adults: a novel insight for the second-meal phenomenon. Am J Clin Nutr. 2018;108(2):332-342. doi:10.1093/ajcn/nqy086
  3. Andrade L, Lee KM, Sylvetsky AC, Kirkpatrick SI. Low-calorie sweeteners and human health: a rapid review of systematic reviews. Nutr Rev. 2021 Sep 7;79(10):1145-1164. doi: 10.1093/nutrit/nuaa123. PMID: 33236063.
  4. Ashtary-Larky D, Bagheri R, Asbaghi O, Tinsley GM, Kooti W, Abbasnezhad A, Afrisham R, Wong A. Effects of resistance training combined with a ketogenic diet on body composition: a systematic review and meta-analysis. Crit Rev Food Sci Nutr. 2021 Feb 24:1-16. doi: 10.1080/10408398.2021.1890689. Epub ahead of print. PMID: 33624538.
  5. Atkinson FS, Brand-Miller JC, Foster-Powell K, Buyken AE, Goletzke J. International tables of glycemic index and glycemic load values 2021: a systematic review. Am J Clin Nutr. 2021 Nov 8;114(5):1625-1632. doi: 10.1093/ajcn/nqab233. PMID: 34258626.
  6. Baker-Smith CM, de Ferranti SD, Cochran WJ; COMMITTEE ON NUTRITION, SECTION ON GASTROENTEROLOGY, HEPATOLOGY, AND NUTRITION. The Use of Nonnutritive Sweeteners in Children. Pediatrics. 2019 Nov;144(5):e20192765. doi: 10.1542/peds.2019-2765. PMID: 31659005.
  7. Bhagavathula AS, Rahmani J, Vidyasagar K, Tesfaye W, Khubchandani J. Sweetened beverage consumption and risk of cardiovascular mortality: A systematic review and meta-analysis. Diabetes Metab Syndr. 2022 Apr;16(4):102462. doi: 10.1016/j.dsx.2022.102462. Epub 2022 Mar 15. PMID: 35325785.
  8. Blaak EE, Riccardi G, Cho L. Carbohydrates: Separating fact from fiction. Atherosclerosis. 2021 Jul;328:114-123. doi: 10.1016/j.atherosclerosis.2021.03.025. Epub 2021 Mar 28. PMID: 33832770.
  9. Chiavaroli L, Cheung A, Ayoub-Charette S, Ahmed A, Lee D, Au-Yeung F, Qi X, Back S, McGlynn N, Ha V, Lai E, Khan TA, Blanco Mejia S, Zurbau A, Choo VL, de Souza RJ, Wolever TM, Leiter LA, Kendall CW, Jenkins DJ, Sievenpiper JL. Important food sources of fructose-containing sugars and adiposity: A systematic review and meta-analysis of controlled feeding trials. Am J Clin Nutr. 2023 Apr;117(4):741-765. doi: 10.1016/j.ajcnut.2023.01.023. Epub 2023 Feb 23. PMID: 36842451.
  10. Dalenberg JR, Patel BP, Denis R, Veldhuizen MG, Nakamura Y, Vinke PC, Luquet S, Small DM. Short-Term Consumption of Sucralose with, but Not without, Carbohydrate Impairs Neural and Metabolic Sensitivity to Sugar in Humans. Cell Metab. 2020 Mar 3;31(3):493-502.e7. doi: 10.1016/j.cmet.2020.01.014. PMID: 32130881.
  11. Fardet A, Richonnet C, Mazur A. Association between consumption of fruit or processed fruit and chronic diseases and their risk factors: a systematic review of meta-analyses. Nutr Rev. 2019;77(6):376-387. doi:10.1093/nutrit/nuz004
  12. Gaesser GA, Miller Jones J, Angadi SS. Perspective: Does Glycemic Index Matter for Weight Loss and Obesity Prevention? Examination of the Evidence on “Fast” Compared with “Slow” Carbs. Adv Nutr. 2021 Dec 1;12(6):2076-2084. doi: 10.1093/advances/nmab093. PMID: 34352885; PMCID: PMC8634321.
  13. Greyling A, Appleton KM, Raben A, Mela DJ. Acute glycemic and insulinemic effects of low-energy sweeteners: a systematic review and meta-analysis of randomized controlled trials. Am J Clin Nutr. 2020 Oct 1;112(4):1002-1014. doi: 10.1093/ajcn/nqaa167. PMID: 32672338.
  14. Hall KD, Ayuketah A, Brychta R, Cai H, Cassimatis T, Chen KY, Chung ST, Costa E, Courville A, Darcey V, Fletcher LA, Forde CG, Gharib AM, Guo J, Howard R, Joseph PV, McGehee S, Ouwerkerk R, Raisinger K, Rozga I, Stagliano M, Walter M, Walter PJ, Yang S, Zhou M. Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake. Cell Metab. 2020 Oct 6;32(4):690. doi: 10.1016/j.cmet.2020.08.014. Erratum for: Cell Metab. 2019 Jul 2;30(1):67-77.e3. PMID: 33027677.
  15. Harrold JA, Hill S, Radu C, Thomas P, Thorp P, Hardman CA, Christiansen P, Halford JCG. Effects of non-nutritive sweetened beverages versus water after a 12-week weight-loss program: A randomized controlled trial. Obesity (Silver Spring). 2023 Aug;31(8):1996-2008. doi: 10.1002/oby.23796. PMID: 37475684.
  16. Hedrick VE, Nieto C, Grilo MF, Sylvetsky AC. Non-sugar sweeteners: helpful or harmful? The challenge of developing intake recommendations with the available research. BMJ. 2023 Oct 9;383:e075293. doi: 10.1136/bmj-2023-075293. PMID: 37813435.
  17. Higgins KA, Considine RV, Mattes RD. Aspartame Consumption for 12 Weeks Does Not Affect Glycemia, Appetite, or Body Weight of Healthy, Lean Adults in a Randomized Controlled Trial. J Nutr. 2018 Apr 1;148(4):650-657. doi: 10.1093/jn/nxy021. PMID: 29659969.
  18. Higgins KA, Mattes RD. A randomized controlled trial contrasting the effects of 4 low-calorie sweeteners and sucrose on body weight in adults with overweight or obesity. Am J Clin Nutr. 2019 May 1;109(5):1288-1301. doi: 10.1093/ajcn/nqy381. PMID: 30997499.
  19. Jayedi A, Soltani S, Jenkins D, Sievenpiper J, Shab-Bidar S. Dietary glycemic index, glycemic load, and chronic disease: an umbrella review of meta-analyses of prospective cohort studies. Crit Rev Food Sci Nutr. 2020 Dec 1:1-10. doi: 10.1080/10408398.2020.1854168. Epub ahead of print. PMID: 33261511.
  20. Jayedi A, Zeraattalab-Motlagh S, Jabbarzadeh B, Hosseini Y, Jibril AT, Shahinfar H, Mirrafiei A, Hosseini F, Bidar SS. Dose-dependent effect of carbohydrate restriction for type 2 diabetes management: a systematic review and dose-response meta-analysis of randomized controlled trials. Am J Clin Nutr. 2022 May 10:nqac066. doi: 10.1093/ajcn/nqac066. Epub ahead of print. PMID: 35537861.
  21. Jo U, Park K. Carbohydrate Intake and Risk of Cardiovascular Disease: A Systematic Review and Meta-Analysis of Prospective Studies. Nutrients. 2023 Apr 2;15(7):1740. doi: 10.3390/nu15071740. PMID: 37049580; PMCID: PMC10096555.
  22. Jones JM, García CG, Braun HJ. Perspective: Whole and Refined Grains and Health-Evidence Supporting “Make Half Your Grains Whole”. Adv Nutr. 2020;11(3):492-506. doi:10.1093/advances/nmz114
  23. Khan TA, Sievenpiper JL. Low-energy sweeteners and cardiometabolic health: is there method in the madness? Am J Clin Nutr. 2020 Oct 1;112(4):917-919. doi: 10.1093/ajcn/nqaa260. PMID: 32936875.
  24. Khan TA, Sievenpiper JL. Low-Calorie Sweeteners with Carbohydrate Do Not Impair Insulin Sensitivity in Humans: Re-analysis Highlighting the Importance of the Comparator. Cell Metab. 2021 Feb 2;33(2):225-226. doi: 10.1016/j.cmet.2020.10.024. PMID: 33535094.
  25. Khan TA, Lee JJ, Ayoub-Charette S, Noronha JC, McGlynn N, Chiavaroli L, Sievenpiper JL. WHO guideline on the use of non-sugar sweeteners: a need for reconsideration. Eur J Clin Nutr. 2023 Sep 18. doi: 10.1038/s41430-023-01314-7. Epub ahead of print. PMID: 37723261.
  26. Laviada-Molina H, Molina-Segui F, Pérez-Gaxiola G, Cuello-García C, Arjona-Villicaña R, Espinosa-Marrón A, Martinez-Portilla RJ. Effects of nonnutritive sweeteners on body weight and BMI in diverse clinical contexts: Systematic review and meta-analysis. Obes Rev. 2020 Jul;21(7):e13020. doi: 10.1111/obr.13020. Epub 2020 Mar 25. PMID: 32216045.
  27. Makarem N, Bandera EV, Nicholson JM, Parekh N. Consumption of Sugars, Sugary Foods, and Sugary Beverages in Relation to Cancer Risk: A Systematic Review of Longitudinal Studies. Annu Rev Nutr. 2018;38:17-39. doi:10.1146/annurev-nutr-082117-051805
  28. McGlynn ND, Khan TA, Wang L, Zhang R, Chiavaroli L, Au-Yeung F, Lee JJ, Noronha JC, Comelli EM, Blanco Mejia S, Ahmed A, Malik VS, Hill JO, Leiter LA, Agarwal A, Jeppesen PB, Rahelic D, Kahleová H, Salas-Salvadó J, Kendall CWC, Sievenpiper JL. Association of Low- and No-Calorie Sweetened Beverages as a Replacement for Sugar-Sweetened Beverages With Body Weight and Cardiometabolic Risk: A Systematic Review and Meta-analysis. JAMA Netw Open. 2022 Mar 1;5(3):e222092. doi: 10.1001/jamanetworkopen.2022.2092. PMID: 35285920.
  29. McSwiney FT, Doyle L, Plews DJ, Zinn C. Impact Of Ketogenic Diet On Athletes: Current Insights. Open Access J Sports Med. 2019;10:171-183. Published 2019 Nov 15. doi:10.2147/OAJSM.S180409
  30. Mehat K, Chen Y, Corpe CP. The Combined Effects of Aspartame and Acesulfame-K Blends on Appetite: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. Adv Nutr. 2022 Dec 22;13(6):2329-2340. doi: 10.1093/advances/nmac072. PMID: 36056917; PMCID: PMC9776645.
  31. Meng Y, Li S, Khan J, Dai Z, Li C, Hu X, Shen Q, Xue Y. Sugar- and Artificially Sweetened Beverages Consumption Linked to Type 2 Diabetes, Cardiovascular Diseases, and All-Cause Mortality: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies. Nutrients. 2021 Jul 30;13(8):2636. doi: 10.3390/nu13082636. PMID: 34444794; PMCID: PMC8402166.
  32. Movahedian M, Golzan SA, Asbaghi O, Prabahar K, Hekmatdoost A. Assessing the impact of non-nutritive sweeteners on anthropometric indices and leptin levels in adults: A GRADE-assessed systematic review, meta-analysis, and meta-regression of randomized clinical trials. Crit Rev Food Sci Nutr. 2023 Jul 13:1-18. doi: 10.1080/10408398.2023.2233615. Epub ahead of print. PMID: 37440689.
  33. Murray B, Rosenbloom C. Fundamentals of glycogen metabolism for coaches and athletes. Nutr Rev. 2018;76(4):243-259. doi:10.1093/nutrit/nuy001
  34. Orku SE, Suyen G, Bas M. The effect of regular consumption of four low- or no-calorie sweeteners on glycemic response in healthy women: A randomized controlled trial. Nutrition. 2023 Feb;106:111885. doi: 10.1016/j.nut.2022.111885. Epub 2022 Nov 1. PMID: 36470113.
  35. Perrar I, Alexy U. Comments on: “The role of dietary sugars in health: molecular composition or just calories?”. Eur J Clin Nutr. 2019;73(9):1323-1324. doi:10.1038/s41430-019-0456-3
  36. Porrata-Maury C, Hernández-Triana M, Ruiz-Álvarez V, et al. Ma-Pi 2 macrobiotic diet and type 2 diabetes mellitus: pooled analysis of short-term intervention studies. Diabetes Metab Res Rev. 2014;30 Suppl 1:55-66. doi:10.1002/dmrr.2519
  37. Prinz P. The role of dietary sugars in health: molecular composition or just calories?. Eur J Clin Nutr. 2019a;73(9):1216-1223. doi:10.1038/s41430-019-0407-z
  38. Prinz P. Author’s reply to: Comments on “The role of dietary sugars in health: molecular composition or just calories?”. Eur J Clin Nutr. 2019b;73(9):1325-1326. doi:10.1038/s41430-019-0457-2
  39. Reynolds A, Mann J, Cummings J, Winter N, Mete E, Te Morenga L. Carbohydrate quality and human health: a series of systematic reviews and meta-analyses [published correction appears in Lancet. 2019 Feb 2;393(10170):406]. Lancet. 2019;393(10170):434-445. doi:10.1016/S0140-6736(18)31809-9
  40. Rippe JM, Angelopoulos TJ. Sugars and Health Controversies: What Does the Science Say?. Adv Nutr. 2015;6(4):493S-503S. Published 2015 Jul 7. doi:10.3945/an.114.007195
  41. Rogers PJ, Appleton KM. The effects of low-calorie sweeteners on energy intake and body weight: a systematic review and meta-analyses of sustained intervention studies. Int J Obes (Lond). 2021 Mar;45(3):464-478. doi: 10.1038/s41366-020-00704-2. Epub 2020 Nov 9. Erratum in: Int J Obes (Lond). 2021 May 27;: PMID: 33168917.
  42. Romo-Romo A, Aguilar-Salinas CA, Brito-Córdova GX, Gómez-Díaz RA, Almeda-Valdes P. Sucralose decreases insulin sensitivity in healthy subjects: a randomized controlled trial. Am J Clin Nutr. 2018 Sep 1;108(3):485-491. doi: 10.1093/ajcn/nqy152. PMID: 30535090.
  43. Sartorius K, Sartorius B, Madiba TE, Stefan C. Does high-carbohydrate intake lead to increased risk of obesity? A systematic review and meta-analysis. BMJ Open. 2018;8(2):e018449. Published 2018 Feb 8. doi:10.1136/bmjopen-2017-018449
  44. Seid H, Rosenbaum M. Low Carbohydrate and Low-Fat Diets: What We Don’t Know and Why we Should Know It. Nutrients. 2019 Nov 12;11(11):2749. doi: 10.3390/nu11112749. PMID: 31726791; PMCID: PMC6893678.
  45. Sherrier M, Li H. The impact of keto-adaptation on exercise performance and the role of metabolic-regulating cytokines. Am J Clin Nutr. 2019;110(3):562-573. doi:10.1093/ajcn/nqz145
  46. Suez J, Cohen Y, Valdés-Mas R, Mor U, Dori-Bachash M, Federici S, Zmora N, Leshem A, Heinemann M, Linevsky R, Zur M, Ben-Zeev Brik R, Bukimer A, Eliyahu-Miller S, Metz A, Fischbein R, Sharov O, Malitsky S, Itkin M, Stettner N, Harmelin A, Shapiro H, Stein-Thoeringer CK, Segal E, Elinav E. Personalized microbiome-driven effects of non-nutritive sweeteners on human glucose tolerance. Cell. 2022 Sep 1;185(18):3307-3328.e19. doi: 10.1016/j.cell.2022.07.016. Epub 2022 Aug 19. PMID: 35987213.
  47. Sylvetsky AC, Edelstein SL, Walford G, et al. A High-Carbohydrate, High-Fiber, Low-Fat Diet Results in Weight Loss among Adults at High Risk of Type 2 Diabetes. J Nutr. 2017;147(11):2060-2066. doi:10.3945/jn.117.252395
  48. Sylvetsky AC, Rother KI. Nonnutritive Sweeteners in Weight Management and Chronic Disease: A Review. Obesity (Silver Spring). 2018 Apr;26(4):635-640. doi: 10.1002/oby.22139. PMID: 29570245; PMCID: PMC5868411.
  49. Tobiassen PA, Køster-Rasmussen R. Substitution of sugar-sweetened beverages with non-caloric alternatives and weight change: A systematic review of randomized trials and meta-analysis. Obes Rev. 2023 Oct 25:e13652. doi: 10.1111/obr.13652. Epub ahead of print. PMID: 37880814.
  50. Turati F, Galeone C, Augustin LSA, La Vecchia C. Glycemic Index, Glycemic Load and Cancer Risk: An Updated Meta-Analysis. Nutrients. 2019;11(10):2342. Published 2019 Oct 2. doi:10.3390/nu11102342
  51. van Baak MA. Dietary carbohydrates and weight loss maintenance. Curr Opin Clin Nutr Metab Care. 2021 Jul 1;24(4):354-358. doi: 10.1097/MCO.0000000000000758. PMID: 33883419.
  52. Vargas S, Romance R, Petro JL, et al. Efficacy of ketogenic diet on body composition during resistance training in trained men: a randomized controlled trial. J Int Soc Sports Nutr. 2018;15(1):31. Published 2018 Jul 9. doi:10.1186/s12970-018-0236-9
  53. Vega-López S, Ausman LM, Griffith JL, Lichtenstein AH. Interindividual variability and intra-individual reproducibility of glycemic index
    values for commercial white bread. Diabetes Care. 2007;30(6):1412-1417. doi:10.2337/dc06-1598
  54. Vega-López S, Venn BJ, Slavin JL. Relevance of the Glycemic Index and Glycemic Load for Body Weight, Diabetes, and Cardiovascular Disease. Nutrients. 2018;10(10):1361. Published 2018 Sep 22. doi:10.3390/nu10101361
  55. Veit M, van Asten R, Olie A, Prinz P. The role of dietary sugars, overweight, and obesity in type 2 diabetes mellitus: a narrative review. Eur J Clin Nutr. 2022 Mar 21. doi: 10.1038/s41430-022-01114-5. Epub ahead of print. PMID: 35314768.
  56. Wallace TC, Bailey RL, Blumberg JB, Burton-Freeman B, Chen CO, Crowe-White KM, Drewnowski A, Hooshmand S, Johnson E, Lewis R, Murray R, Shapses SA, Wang DD. Fruits, vegetables, and health: A comprehensive narrative, umbrella review of the science and recommendations for enhanced public policy to improve intake. Crit Rev Food Sci Nutr. 2020;60(13):2174-2211. doi: 10.1080/10408398.2019.1632258. Epub 2019 Jul 3. PMID: 31267783.
  57. Wang Y, Zhao R, Wang B, Zhao C, Zhu B, Tian X. The Dose-Response Associations of Sugar-Sweetened Beverage Intake with the Risk of Stroke, Depression, Cancer, and Cause-Specific Mortality: A Systematic Review and Meta-Analysis of Prospective Studies. Nutrients. 2022 Feb 12;14(4):777. doi: 10.3390/nu14040777. PMID: 35215425; PMCID: PMC8875574.
  58. Wilk K, Korytek W, Pelczyńska M, Moszak M, Bogdański P. The Effect of Artificial Sweeteners Use on Sweet Taste Perception and Weight Loss Efficacy: A Review. Nutrients. 2022 Mar 16;14(6):1261. doi: 10.3390/nu14061261. PMID: 35334918; PMCID: PMC8954878.
  59. Witkowski M, Nemet I, Alamri H, Wilcox J, Gupta N, Nimer N, Haghikia A, Li XS, Wu Y, Saha PP, Demuth I, König M, Steinhagen-Thiessen E, Cajka T, Fiehn O, Landmesser U, Tang WHW, Hazen SL. The artificial sweetener erythritol and cardiovascular event risk. Nat Med. 2023 Mar;29(3):710-718. doi: 10.1038/s41591-023-02223-9. Epub 2023 Feb 27. PMID: 36849732.
  60. Wyatt P, Berry SE, Finlayson G, O’Driscoll R, Hadjigeorgiou G, Drew DA, Khatib HA, Nguyen LH, Linenberg I, Chan AT, Spector TD, Franks PW, Wolf J, Blundell J, Valdes AM. Postprandial glycaemic dips predict appetite and energy intake in healthy individuals. Nat Metab. 2021 Apr;3(4):523-529. doi: 10.1038/s42255-021-00383-x. Epub 2021 Apr 12. Erratum in: Nat Metab. 2021 Jul;3(7):1032. PMID: 33846643; PMCID: PMC7610681.
  61. Yan RR, Bun Chan C, Chun Yu Louie J. Current World Health Organization recommendation to reduce free sugar intake from all sources to below 10% of daily energy intake for supporting overall health is not well-supported by available evidence. Am J Clin Nutr. 2022 Apr 5:nqac084. doi: 10.1093/ajcn/nqac084. Epub ahead of print. PMID: 35380611.
  62. Yang Q, Lang X, Li W, Liang Y. The effects of low-fat, high-carbohydrate diets vs. low-carbohydrate, high-fat diets on weight, blood pressure, serum liquids and blood glucose: a systematic review and meta-analysis. Eur J Clin Nutr. 2022 Jan;76(1):16-27. doi: 10.1038/s41430-021-00927-0. Epub 2021 Jun 24. PMID: 34168293.
  63. Zeevi D, Korem T, Zmora N, et al. Personalized Nutrition by Prediction of Glycemic Responses. Cell. 2015;163(5):1079-1094. doi:10.1016/j.cell.2015.11.001
  64. Zhang R, Noronha JC, Khan TA, McGlynn N, Back S, Grant SM, Kendall CWC, Sievenpiper JL. The Effect of Non-Nutritive Sweetened Beverages on Postprandial Glycemic and Endocrine Responses: A Systematic Review and Network Meta-Analysis. Nutrients. 2023 Feb 20;15(4):1050. doi: 10.3390/nu15041050. PMID: 36839408; PMCID: PMC9965414.
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