Diets and Body Composition

As a trainer, I am often asked about various diets and how to manipulate body composition. Unfortunately, there is so much contradictory information circulating online that best practices often become unclear. While nutritional science is a constantly evolving field, we can certainly draw out well-established principles from the current breadth of available literature. My attempt in this article will be to clarify some common misconceptions and provide practical, evidence-based recommendations on nutrition.

DIETS — WHAT WORKS?

For the purpose of this article, we will focus on dietary interventions used for the purpose of changing body composition — such as losing body fat or gaining/retaining lean mass — rather than one used to treat a medical condition or for moral/ethical reasons. There are many popular diets ranging from more general approaches such as low-carb to ketogenic, carnivore, paleo, or vegan. These diets focus on one primary intervention, namely, changing what you eat. Other approaches, such as “flexible dieting” or IIFYM (if it fits your macros) focus solely on how much you consume of each macronutrient. More recently, intermittent fasting and time-restricted feeding have gained popularity. These dietary strategies emphasize when you eat by adhering to daily fasting and feeding windows. You’ve likely heard others touting the success of several if not all of these methods. So, how do you know what really works and more importantly, what will work for you? Below I will break down what the evidence says about how diets actually work and help you understand which approach may be the best fit for you.

ENERGY BALANCE

Energy balance refers to the net difference between the energy you consume and the energy you expend. Another way of putting is “calories in - calories out”, or, CICO. In its most basic form, this is the equation that governs the effect of any diet on weight gain or loss (Aragon et al., 2017). When more calories are consistently consumed than expended, people gain weight. When more calories are consistently burned than consumed, people lose weight. Think about some of the examples given above. On their face, a ketogenic diet or intermittent fasting may not seem to be concerned with energy balance. However, when resulting in weight loss, both of these diets have a net effect of reducing total caloric intake; whether by nearly eliminating a macronutrient (carbohydrate), or by vastly decreasing the amount of time within the day that an individual is permitted to eat. Simply put, monitoring what you eat or when you eat can end up affecting how much you eat.

With this in mind, the “calories in” side of the equation ends up being largely a preference decision. There are, however, aspects of certain diets that may help some people adhere to that diet more easily than others. For example, ketogenic diets have been shown to have appetite-suppressing potential, wherein adherents have spontaneously reduced average daily caloric intake without purposeful restriction (Aragon et al., 2017). On the other hand, a higher carbohydrate diet may better support the energy demands of a person engaged in regular intense training, and therefore be easier to stick with for that individual. Variations of intermittent caloric restriction have not been shown to provide additional improvements in body composition when compared to daily restriction, but may best fit the lifestyle of an individual, promoting a better adherence (Aragon et al., 2017). Dietary frameworks should therefore be considered based upon the preferences and specific goals of the individual while maintaining the general principles which govern body composition.

To further understand energy balance, we must now look at the “calories out” side of the equation. To help visualize this, please refer to the graph below from Trexler et al., (2014): Calories

Calories out, or, total daily energy expenditure (TDEE) is broken down into four categories. The largest component of TDEE is your basal metabolic rate (BMR). BMR — while technically referring to the energetic cost of survival at rest in a overnight fasted, postabsorptive state — is generally used to refer to resting energy expenditure (REE), representing calories burned at rest in a fasted state during any time of the day (Aragon et al., 2017). REE typically accounts for 60-70% of daily energy expenditure and is estimated by factoring in your sex, height, weight, and age (Aragon et al., 2017).

The second largest component of TDEE is non-exercise activity thermogenesis (NEAT), comprising the calories burned moving around throughout the day independent of purposeful exercise; such as leisure, occupation, or unconscious movement (Aragon et al., 2017). The large contribution of NEAT to TDEE can often be overlooked, and can vary widely from person to person — up to 2,000 calories per day for individuals of similar size (Aragon et al., 2017). Awareness of the importance of NEAT to overall energy expenditure as well as the tendency of NEAT to decrease with consistent periods of caloric restriction and increase during periods of surplus is key to successful manipulation and maintenance of body composition (Aragon et al., 2017).

For a sedentary individual, the thermic effect of food (TEF) may represent the third largest component of TDEE. TEF refers to the energy used for digesting and metabolizing nutrients. It is a relatively static measure, but can be influenced by certain eating behaviors. Although individual variance exists, protein has been consistently shown to have a greater thermic effect compared to carbohydrate and fat (Aragon et al., 2017). In addition, the degree to which foods have been processed and refined may reduce their thermic effect (Aragon et al., 2017).

Exercise activity thermogenesis (EAT) refers to calories burned as a result of intentional exercise. While often thought of as a primary driver of weight loss, EAT typically accounts for only 15-30% of TDEE (Aragon et al., 2017). Apart from individuals who regularly perform very high volume intense exercise (think triathletes), EAT represents one of the smaller contributors to TDEE, albeit one that is under direct control of the individual. Choices in modality of exercise can play an important role in promoting body composition changes, with certain forms of exercise, such as resistance training, being favorable to the acquisition of lean muscle mass (Benito et al., 2020).

MACRONUTRIENTS

If energy balance can be thought of as the base of the nutritional pyramid, then macronutrient distribution can be thought of as the next layer. While the net difference between caloric intake and expenditure is the primary driver of weight gain and loss, macronutrient intake -- and protein in particular -- can have significant effects on body composition changes. It is well known that a high protein intake in combination with a caloric surplus and resistance training promotes growth in skeletal muscle mass (Jäger et al., 2017). What may be lesser known, is that high protein intakes of 2-3 times the recommended dietary allowance of 0.8 g/kg/day, combined with resistance training, have been repeatedly shown to maximize fat loss while maximizing the maintenance of fat free muscle mass in hypocaloric conditions (Jäger et al., 2017). A high-protein diet has thus been shown to promote favorable body composition changes under conditions of both a calorie surplus and deficit. In addition, protein is considered the most satiating macronutrient, meaning greater perceived fullness is associated with protein consumption compared to fat or carbohydrate (Leidy et al., 2015). The International Society of Sports Nutrition recommends that exercising individuals consume 1.4-2.0 grams of protein/kg body weight/day, however there is evidence to suggest that even higher intakes may promote favorable body composition changes in resistance-trained individuals (Jäger et al., 2017).

These recommendations should be considered in the context of discussing the macronutrient ratios inherent to each diet, and the advantages or challenges they present. For example, vegan athletes appear to consume less protein on average, and may have to pay special attention to consume a variety of plant protein sources necessary to obtain the quantity of essential amino acids found in animal sources (Rogerson, 2017). As mentioned, very high fat/low carbohydrate diets such as the ketogenic diet have been shown to have appetite suppressing qualities, which may result in lower energy intake when left uncontrolled (Hall & Guo, 2017). However, it is important to note that when analyzing the breadth of controlled feeding studies, a systematic review by Hall & Guo (2017) found that there was no physiologically significant difference in fat loss between isocaloric diets with various ratios of carbohydrate and fat when protein was matched. This means that while certain distributions of carbohydrate and fat may be preferable to an individual for specific health or performance reasons, as long as the calories and protein consumed are equated, altering the ratios of carbohydrate or fat has not been shown to have an effect on total body fat. These findings invalidate common theories such as the carbohydrate-insulin model of obesity often espoused by low-carbohydrate diet proponents.

NUTRIENT TIMING

For athletes or those interested in manipulating their nutrition to achieve more extreme results, tools such as nutrient timing can be considered. Nutrient timing encompasses the strategic timing of whole food and supplemental macronutrient consumption to meet specific needs, typically related to performance. For example, while meeting the recommended total daily protein intake is of primary importance, muscle protein synthesis is most optimally stimulated by regular protein feedings of 20-40 g every 3-4 hours (Kersick et al., 2017). The degree of change attributed to various timing of nutrients may or may not be relevant to each person. In general, nutrient timing is an important consideration of any elite athlete attempting to achieve peak performance. In relation to dietary adherence, more precise nutrient timing requires more planning and preparation, and if not necessary may be overburdening. However, attention to the timing of nutrient intake in the presence of an exercise program may better support the training, and improve body composition changes.

FOOD COMPOSITION

While it is possible to meet energy intake goals and macronutrient requirements using a variety of food sources, it is important to keep in mind that whole foods often serve as a richer source of micronutrients and more positively affect the gut microbiome when compared to highly processed foods (Zinöcker & Lindseth, 2018). Availability and consumption of ultra-processed foods -- defined as foods made by industrial formulations of ingredients derived from food or food constituents, or synthesized in laboratories from food substrates -- has been positively associated with increased risks of obesity and lower dietary nutritional quality (Zinöcker & Lindseth, 2018). Ultra-processed foods are often characterized by lower nutrient density, and higher energy density per calorie, compared to unprocessed foods (Gupta et al., 2019). It is also argued that factors introduced during food processing may produce inflammatory responses in the body by distributing the gut microbiota (Zinöcker & Lindseth, 2018). Regardless, it is well understood that the industrial manufacturing of processed foods includes measures such as flavor enhancements and color additives intended to make foods hyper-palatable (Zinöcker & Lindseth, 2018). This fact is reflected in controlled trials in which individuals exposed to ultra-processed diets consume more calories ad libitum than those exposed to non-processed diets. In a randomized controlled trial conducted by Hall et al., (2019) two groups were presented with either an ultra-processed or unprocessed diet matched for calories, sugar, fat, fiber, and macronutrients, and instructed to eat as much as desired for two weeks. The findings of the study support the idea that ultra-processed foods may be more prone to be overeaten, as subjects consumed roughly 500 calories more per day on the ultra-processed diet and gained body weight, compared the unprocessed group which lost body weight (Hall et al., 2019). Awareness of these factors in combination with the importance of energy balance to body composition would suggest that ultra-processed foods are not an ideal choice to promote caloric restriction and should be consumed in limited quantities in that context.

SUPPLEMENTS

The dietary supplement industry offers a broad range of products from vitamins and minerals to performance-enhancing supplements and convenience supplements. The use of vitamin and mineral supplements to promote overall health or correct nutrient deficiencies is an important consideration but one that falls outside the scope of this article and is best evaluated on an individual basis. Few performance-enhancing supplements exist with a strong evidence base to support their efficacy. However, proven supplements such as creatine monohydrate or protein supplements may aid in achieving body composition goals by augmenting physiological processes during training, or by providing additional macronutrients to meet daily targets or deliver those nutrients with precise timing (Kersick et al., 2018). Convenience supplements such as shakes and bars can serve as a good alternative to fast food or foods of lower nutritional quality when fresh whole foods are not easily accessible (Kersick et al., 2018). These products can also be useful for providing nutrients around workouts but should not be viewed as a consistent replacement for proper meals (Kersick et al, 2018).

CONCLUSION

For the average person who wishes to maintain a healthy body weight and see results from their workouts, consistent attention to energy balance and adequate protein intake will likely cover a majority of the bases. The benefit of this “flexible” approach is that it is minimally restrictive, and allows you to eat any foods that you enjoy in moderation. Every diet geared towards fat loss contains some version of restriction, in order to impose the necessary caloric deficit. The key for most people is to find the form of restriction that feels the least restricting and best promotes adherence to the diet. While some evidence suggests that diets which impose more stringent restraints on certain foods or food groups are more likely to cause cravings and overeating (Polivy et al., 2005; Stirling & Yeomans, 2003), each person has different preferences and mindsets. With attention to the key principles outlined throughout this article, individuals should choose a diet that they are best able to adhere to, as this is seen as a key indicator of success (Gibson & Sainsbury, 2017). The timing of nutrients should be considered in light of the goals and training demands of the individual. Including a variety of whole-foods in the diet will promote a healthy gut and adequate consumption of nutrients, and may deter overeating. Finally, dietary supplements can be used as a convenient means to address specific objectives or remaining nutritional deficiencies.

References:

Aragon, A. A., Schoenfeld, B. J., Wildman, R., Kleiner, S., VanDusseldorp, T., Taylor, L., Earnest, C. P., Arciero, P. J., Wilborn, C., Kalman, D. S., Stout, J. R., Willoughby, D. S., Campbell, B., Arent, S. M., Bannock, L., Smith-Ryan, A. E., & Antonio, J. (2017). International Society of Sports Nutrition Position Stand: Diets and body composition. Journal of the International Society of Sports Nutrition, 14(1). https://doi.org/10.1186/s12970-017-0174-y

Benito, P. J., Cupeiro, R., Ramos-Campo, D. J., Alcaraz, P. E., & Rubio-Arias, J. Á. (2020). A systematic review with meta-analysis of the effect of resistance training on whole-body muscle growth in healthy adult males. International Journal of Environmental Research and Public Health, 17(4), 1285. https://doi.org/10.3390/ijerph17041285

Gibson, A. A., & Sainsbury, A. (2017). Strategies to Improve Adherence to Dietary Weight Loss Interventions in Research and Real-World Settings. Behavioral sciences (Basel, Switzerland), 7(3), 44. https://doi.org/10.3390/bs7030044

Gupta, S., Hawk, T., Aggarwal, A., & Drewnowski, A. (2019). Characterizing ultra-processed foods by energy density, nutrient density, and cost. Frontiers in Nutrition, 6. https://doi.org/10.3389/fnut.2019.00070

Jäger, R., Kerksick, C. M., Campbell, B. I., Cribb, P. J., Wells, S. D., Skwiat, T. M., Purpura, M., Ziegenfuss, T. N., Ferrando, A. A., Arent, S. M., Smith-Ryan, A. E., Stout, J. R., Arciero, P. J., Ormsbee, M. J., Taylor, L. W., Wilborn, C. D., Kalman, D. S., Kreider, R. B., Willoughby, D. S., … Antonio, J. (2017). International Society of Sports Nutrition Position Stand: Protein and exercise. Journal of the International Society of Sports Nutrition, 14(1). https://doi.org/10.1186/s12970-017-0177-8

Leidy, H. J., Clifton, P. M., Astrup, A., Wycherley, T. P., Westerterp-Plantenga, M. S., Luscombe-Marsh, N. D., Woods, S. C., & Mattes, R. D. (2015). The role of protein in weight loss and maintenance. The American Journal of Clinical Nutrition, 101(6). https://doi.org/10.3945/ajcn.114.084038

Kerksick, C. M., Arent, S., Schoenfeld, B. J., Stout, J. R., Campbell, B., Wilborn, C. D., Taylor, L., Kalman, D., Smith-Ryan, A. E., Kreider, R. B., Willoughby, D., Arciero, P. J., VanDusseldorp, T. A., Ormsbee, M. J., Wildman, R., Greenwood, M., Ziegenfuss, T. N., Aragon, A. A., & Antonio, J. (2017). International Society of Sports Nutrition Position Stand: Nutrient Timing. Journal of the International Society of Sports Nutrition, 14(1). https://doi.org/10.1186/s12970-017-0189-4

Kerksick, C. M., Wilborn, C. D., Roberts, M. D., Smith-Ryan, A., Kleiner, S. M., Jäger, R., Collins, R., Cooke, M., Davis, J. N., Galvan, E., Greenwood, M., Lowery, L. M., Wildman, R., Antonio, J., & Kreider, R. B. (2018). ISSN Exercise & Sports Nutrition Review update: Research & recommendations. Journal of the International Society of Sports Nutrition, 15(1). https://doi.org/10.1186/s12970-018-0242-y

Hall, K. D., Ayuketah, A., Brychta, R., Cai, H., Cassimatis, T., Chen, K. Y., Chung, S. T., Costa, E., Courville, A., Darcey, V., Fletcher, L. A., Forde, C. G., Gharib, A. M., Guo, J., Howard, R., Joseph, P. V., McGehee, S., Ouwerkerk, R., Raisinger, K., … Zhou, M. (2019). Ultra-processed diets cause excess calorie intake and weight gain: An inpatient randomized controlled trial of AD Libitum Food Intake. Cell Metabolism, 30(1). https://doi.org/10.1016/j.cmet.2019.05.008

Polivy, J., Coleman, J., & Herman, C. P. (2005). The effect of deprivation on food cravings and eating behavior in restrained and unrestrained eaters. International Journal of Eating Disorders, 38(4), 301–309. https://doi.org/10.1002/eat.20195

Rogerson D. (2017). Vegan diets: practical advice for athletes and exercisers. Journal of the International Society of Sports Nutrition, 14, 36. https://doi.org/10.1186/s12970-017-0192-9

Stirling, L. J., & Yeomans, M. R. (2003). Effect of exposure to a forbidden food on eating in restrained and unrestrained women. International Journal of Eating Disorders, 35(1), 59–68. https://doi.org/10.1002/eat.10232

Trexler, E. T., Smith-Ryan, A. E., & Norton, L. E. (2014). Metabolic adaptation to weight loss: Implications for the athlete. Journal of the International Society of Sports Nutrition, 11(1). https://doi.org/10.1186/1550-2783-11-7

Zinöcker, M. K., & Lindseth, I. A. (2018). The Western Diet-Microbiome-Host Interaction and Its Role in Metabolic Disease. Nutrients, 10(3), 365. https://doi.org/10.3390/nu10030365