Diets and Body Composition

Diets and Body Composition

Summary Points from Position Paper on Diets & Body Composition

            The International Society of Sports Nutrition (ISSN) recently posted a position stand on diets and body composition. The ISSN is a reputable body that publishes timely and quality research on the topic of nutrition for sport and exercise. This position paper summarizes the most recent findings that address nutrition and body composition and only includes research studies that meet specific high quality criteria. The full article was published by Aragon et al. in 2017 in the Journal of the International Society of Sports Nutrition (reference at the bottom); however, I thought I would highlight a few of the key points the article made as at least one or more are likely to be relevant to Icon athletes:

  1. Diets that have the primary goal of reducing fat mass have a sustained calorie deficit at their core. The higher the level of body fat at baseline, the more aggressive one can be with the calorie deficit. However, for lean individuals a slower rate of weight loss will better preserve lean body mass.

Kary’s summary & comments: to lose weight, you need to eat less calories than what you burn. If you are not significantly overweight to start with, aim for a low to moderate calorie deficit (250-500 kcals/day – my preference is 250 kcals) to avoid losing weight from muscle mass and to maintain muscle mass.


  1. Diets that have the goal of increasing lean mass are primarily driven by a sustained calorie surplus which supports an anabolic (= building) environment and meet the increased demands of resistance training. The composition and amount of the surplus (quality and quantity of kcals), as well as the training status of the individual (untrained vs. well-trained) affects the amount and type of weight gain.

Kary’s summary & comments: you can increase muscle mass without a calorie surplus (such as those on the perfector track) but gains will be minimal to moderate. For those on the gainer track and looking to really focus on increased muscle mass, a calorie surplus is needed (= eat more calories than you burn on a daily basis). Approximately 250-500 kcals a day for surplus is ideal to avoid excessive weight gain. It is the kcal surplus that really triggers the anabolic hormones needed for building.

The quality of calories matters as well. Most individuals know to eat more protein, and indeed, upwards to 3 grams per kg of body weight may be beneficial (though some studies to not show added benefit of protein intake greater than 2 g/kg). However, it is also important to increase carbohydrate intake as well. One well-designed study had 2 groups consuming a calorie surplus. Both groups started at 1.6 grams of protein/kg. One group had the surplus come just from carbohydrate, another group had the surplus come from protein and carbohydrate together. The carbohydrate group gained 3.4 kg of lean mass and lost .3 kg of fat mass, the carb + protein group gained 2.9 kg of lean mass and gained .2 kg of fat mass. Differences were not statistically significant but indicated an increase beyond 1.6 g/protein/kg did not improve lean mass gains, but that adding carbohydrate did…


  1. A wide variety of dietary approaches ranging from low-fat (20-35% of calories) to low carbohydrate (including ketogenic diets) diets can be effective for improving body composition.

Kary’s summary & comments: there are many approaches to support weight loss and may include the keto diet, the zone diet, or lowfat diets – one is not necessarily better than the others if the calorie deficit is the same. That being said, if one approach is more sustainable, thus making that calorie deficit easier to achieve and maintain on a day to day basis, then that is likely your best approach. If you find the keto diet sustainable and helps you to reduce your intake, then go for that. An important note: the article specified that the ketogenic diet does not show any performance benefits for high intensity exercise and if anything has hindered performance at high intensities according to the current body of evidence.


  1. Increasing protein intake to amounts greater than current recommendations (up to 2.3-3/1 grams per kg of fat free mass – not total body mass) may improve body composition by maximizing lean mass retention in lean, resistance trained individuals when the individual is following a calorie deficit.

Kary’s summary & comments: there are certainly some interesting research studies out there regarding protein intake. When someone is following a calorie restricted diet, consuming up to 3.1 grams (or more!) may enhance preservation of muscle mass/lean body mass. Protein is also more satiating (= helps us feel full) and has a higher thermic effect (that is, requires more energy to be metabolized). Some studies have even shown when calories were increased by over 800 calories (all coming from protein) weight did not increase.  For those of you looking to lose weight and are on a calorie deficit, consider consuming at least 2 grams protein/kg of body weight.


  1. When combining the research together, intermittent fasting/intermittent calorie restriction research does not demonstrate a significant advantage over daily caloric restriction for improving body composition.

Kary’s summary & comments: specific to the effects on improving body composition, intermittent fasting does not seem to have an advantage over daily caloric restriction (such as a 250-500 calorie deficit a day); some research shows a slight benefit but most does not. There may be other metabolic advantages of intermittent fasting that are still being explored. Some individuals report it is just easier, for example, to restrict calories significantly on 2 days a week and then eat ‘normally’ on the other 5 days (such as with the 5:2 Intermittent Fasting approach) and in that case, if that is more sustainable, than that might be a better approach for that individual – not because it will result in better results than regular calorie restriction, but because it is more sustainable. This is where you need to find what works best for you. I do know a lot of athletes have a hard time training on the fasting days, and the morning after a fasting day, so you want to take into consideration how this might affect your training and performance.


  1. Long-term success of a diet depends upon compliance, as well as the suppression or avoidance of factors that may weaken the effects of a diet such as adaptive thermogenesis.

Kary’s summary & comments: adaptive thermogenesis (AT) is truly an intriguing phenomenon that I actually are area of research that I am interested in.  AT is complex and multifactorial, but to try and simplify it AT describes the decrease in energy expenditure when significant weight has been lost that is not accounted for by loss of metabolic tissue. The exact mechanisms are unclear, but there is some research to indicate that the effects of AT can be mitigated with higher protein intakes. See point #4 above. If you are interested in AT let me know and I can devote an entire blog to this topic!


From: Aragon AASchoenfeld BJWildman RKleiner SVanDusseldorp TTaylor LEarnest CPArciero PJWilborn CKalman DSStout JRWilloughby DSCampbell BArent SMBannock LSmith-Ryan AEAntonio J. International society of sports nutrition position stand: diets and body composition (2017). J Int Soc Sports Nutr. 2017; 14:16.


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