The International Society of Sports Nutrition just released a position stand that reviewed the literature available regarding diet and body composition. You can read it here. For those who want it broken down into more simple terms, I’ve distilled it somewhat into 11 key take home points. While much of this draws on literature from strength and power athletes, it is definitely applicable to the general audience too, given that resistance-based training is one of the best things you can do to support your health and body composition goals.
- There is a vast multitude of diets and within these, several subtypes of diet. Low fat, low carb, higher protein, Mediterranean, low calorie… and these will all work work to reduce body fat given the right conditions. As a practitioner, we need to be familiar of the evidence supporting each diet type to make informed recommendations to the people we interact with, both at an individual and population level. As someone who is interested in losing body fat, know that no ONE diet is going to suit everyone, and if you’re trying to follow something because your mate is too, but you’re not seeing the results, then potentially it’s not the right plan for you. Seems simple when I write it down – but I think important to remind you.
- All body composition assessment methods have strengths and limitations. It’s good to bear in mind the limitations of using just scales as the only indicator, as this doesn’t account for fat mass loss. I’ve had numerous clients basically freak out that they have gained a kilogram overnight because they’ve eaten something high in carbs (causing your body to hold water) or they have done a hard training session (inflamed tissue). It is impossible to gain kilo of fat over a week, let alone a night, but the obsession with scales can make even the most rational person a little … less rational. Thus, if you use the scales, then think about how this makes you feel. And do it at the same time each week, on waking, after you go to the bathroom – etc. IE try to make it consistent. Ditto re: skinfolds – choose a practitioner who is skilled and stick to the same person so any errors are at least consistent errors.
- While it’s not about ‘calories in, calories out’, as that is far too simplistic, we do need to create a deficit in calories to drop body fat. Don’t freak out by the next bit of (evidence-backed, science-informed) information: The more fat you’ve got stored, the quicker you can lose this body fat without losing too much muscle mass by creating a large calorie deficit. The leaner an individual is, it is better if the caloric deficit isn’t as dramatic, to help preserve muscle mass. We can use calorie cycling to do this (ie higher calories for some days, lower for others across the course of 7-14 days, such as the 5:2 approach), or a consistently lower calorie approach, whatever fits in with the individual and their adherence. This study found that working on a weekly reduction of 0.7% of body weight better than 1.4% for preservation of lean muscle tissue.
- A wide range of dietary approaches (low-fat to low-carbohydrate/ketogenic, and all points between) can be similarly effective for improving body composition, and this allows flexibility with programme design, which is great – again, there is no one right approach for everyone. AND there is no one approach that will suit the same individual all the time – context, physical activity, stress, budget etc will all affect the suitability of an eating style that will improve body composition. This in part could explain why Weight Watchers, which helped you drop weight in the past, is not working now – regardless of how many points you are under at the end of the day/week. Being flexible rather than dogmatic will go a long way to finding a plan that suits you. I will also add, however, that something based on minimally processed food contains more nutrients – this will nourish your body and provide nutrients to ensure metabolism, brain and gut health are optimised while shifting excess body fat.
- When protein amounts are matched in the diet, there doesn’t appear to be an approach that reports a meaningful reduction of fat when we look at different macronutrient composition. All are as effective as each other – it’s sustainability which is the factor to consider. If an individual is insulin sensitive, research shows they are going to be able to lose weight on a moderate carbohydrate diet and potentially perform better on that than a lower carbohydrate diet. The reverse is also true. In addition, when adding resistance training to the mix, in some instances insulin sensitivity is improved. Therefore, knowing your metabolic health markers initially can help you determine what dietary approach might work for you.
- However, a ketogenic diet has been shown to have appetite-suppressing potential in part due to its effects on our appetite hormones (as explained in this review), resulting in a spontaneous caloric restriction. That said, for some this may only happen initially and clinically I have seen that this affect appears to wear off. (Note, this is my clinical observation).
- Increasing dietary protein to levels significantly beyond current recommendations for athletic populations (up to 2g/kg body weight) may improve body composition as in line with the ISSN’s position stand. It is also much more satiating for those of us who aren’t athletes, particularly in a restricted calorie state (as I’ve discussed here). There is also evidence that increasing protein in the diet beyond 3g/kg body weight and creating a calorie surplus can increase muscle mass and decrease fat mass simultaneously- I know! It’s like magic! Except very difficult to eat that much protein for a lot of people.
- Time-restricted feeding (which I’ve written about here) combined with resistance training is an emerging area of research that has thus far shown mixed results with respect to body composition (ie see here and here, however eating within that restricted window does allow for improvements in metabolic health. Much like cycling calories, the window of time that people choose to eat should be based on individual preference in a way that is easy to be sustained in everyday life. There is more to gain from having a good resistance-based training programme and adequate protein (in the context of an awesome diet) than worrying if your eating window is 8 hours a day or 9 hours a day.
- Do we starve our metabolism, thus slow it down and lead to fat gain if we restrict calories too much? Only in the context of a restrictive caloric diet and in the absence of resistance training where muscle mass has reduced, and energy expenditure has reduced. This can be mitigated when these are accounted for (see here and here).
- In addition to this, clinically what seems to work well is having a metabolic reset meal, where more fat/carb calories are consumed (which some might call a ‘treat’ or ‘cheat’ meal, particularly in the fitness industry) – this might be 1-2 meals every 7-14 days depending on the individual and their goals.
- There needs to be more research on women, older adults
- There needs to be more research on meal frequency and timing combined with different caloric loads, and with different training regimes.
Despite all of the above, a member of my online nutrition coaching system shared with me her experience with improving overall health (and metabolic markers – prior to embarking on her regime her HbA1c was in ‘pre-diabetic’ range). She found focusing on a higher fat approach, coupled with water fasting helps her control her insulin resistance and overall health much more than focusing on protein intake. While a few years ago this would have set alarm bells ringing in my head, the longer I’m in the game the more I understand that it is so individual as to how someone will respond to a dietary approach. Being willing to experiment with different protocols will help you figure out what works best for you regardless of the research papers.