A research-based review of body composition and racing weight for triathletes.

• Different methods to assess body composition and body fat percentage, and their limitations. 
• How to get to your goal race weight and body composition using three simple principles: appropriate rate of weight loss, appropriate protein intake and staying away from fads. 
• Myths and risks to avoid when it comes to getting lean and losing weight. 
• What is the typical body composition (body fat percentage, weight, Fat Free Mass Index) of elite level triathletes? 
• Periodisation of body composition and racing weight, and the importance of not staying at race weight year round. 

1:00 - 

• A lot of this discussion is based on the Nutrition and Athletic Performance position statement written jointly by the Academy of Nutrition and Dietetics, the Dietitians of Canada and the American College of Sports Medicine. It was published in Medicine, Sports and Exercise Journal in 2016.  
• There is one author representing each of the three entities and they include some of the biggest names in the sports nutrition scientific community. 
• In addition to the three main authors: Louise Burke, Kelly Urban and Travis Thomas, there is a long list of reviewers for the statement who are all experts in the field of nutrition for endurance sports and athletes. 
• International Society of Sports Nutrition (ISSN)'s position stand called 'Diets and body composition', published in the Journal of the International Society of Sports Nutrition in 2017.
• I've also looked at a case study publication by Trent Stellingworth called 'Body composition periodisation in an Olympic level female middle distance runner over a 9 year career' 

5:06 -

• There's no one optimal body composition or weight for a triathlete. It is individual.
  • Two triathletes that are the same height may perform at their own respective bests at different weights or body fat percentages.
• In general, it's beneficial not to carry excess weight.
  • Individualisation comes into what 'excess weight' would be for you.
• If you don't carry excess weight for you, that will lower your energy costs for going at certain speeds on the run, and also uphill on the bike.
  • On the flats on the bike, aerodynamics will usually trump weight.
• If you don't carry excess weight you will also have a favourable ratio of weight to surface area which is beneficial for heat dissipation.
  • When you train for a long time, your body temperature slowly heats up and at a certain point it will prevent you from going faster (or slow you down).
  • This is true in both hot and cold climates.
• Weight loss in itself should never be the end goal, it's only beneficial when you maximise loss of body fat while continuing to preserve muscle mass.
  • The exception would be people transitioning to triathlon who already have a significantly higher muscle mass than average (e.g. body builders).
  • If you carry a lot of muscle mass, to be the best triathlete you can, you may need to lose muscle mass from certain parts of the body that you won't be using in triathlon (e.g. biceps).

7:52 - 

• When discussing body fat percentage, it's important to note that it can be measured in different ways:
  • You can take your own measurements (e.g. waist circumference etc).
  • Gold standard: DEXA scan (dual energy x-ray absorptiometry) which is standardised.
    • However this is expensive and isn't widely available.
    • You may also need a prescription from a doctor for this, depending on where you live.
  • Skin fold measurements, done using skin fold calipers.
    • This measures the thickness of your skin in certain places of your body.
    • It's a great measure of body composition, particularly if you do it at the same place with the same calibrated equipment each time.
    • The disadvantage is that there is usually variation in the measurement and human error.
  • Bioelectrical impedence analysis, completed by having a weak electric current run through your body through stepping on a scale and holding a metal side rail/handle.
• Whatever you do, try to be consistent. Go to the same place each time, and ideally have the same person doing the measurements each time.
• You need to strictly follow the protocols before the measurement, and make sure you follow the same protocol before each subsequent measurement you have.
  • For example: how you fast and hydrate before a test, or how you train before a test.

11:26 - 

• When you want to lose body weight, you need to have an energy deficit in your diet. 
• It is best to do this in the base phase of your training, well away from competition to minimise loss of performance.
• However there are exceptions here, such as the case study being discussed later. This demonstrates the importance of individualisation.

12:50 - 

• You should not be obsessive with weight, body fat, diet, rapid weight loss strategies etc.
  • Performance is multi-factorial.
  • How you train leading up to a race is the most important thing, not how much you weigh on race day.
    • If your weight loss strategy impairs you're training, you won't be able to perform as well.
• There are many ways of losing weight that won't be beneficial.
  • You can loose body weight quickly by having a deficit of water in your body.
  • Depending on how you diet you can loose a lot of glycogen stores and lean mass, neither of which would be beneficial.
    • Glycogen stores are needed for endurance training.
• You should keep a moderate, gradual, slow approach to weight loss. Don't use rapid weight loss strategies.
• Things like starving yourself, purging, doing extra training to reach a caloric deficit, will impair both your health and performance.
• However, losing weight more quickly can be preferred compared to constantly being in a state of low energy availability or energy/caloric restriction mode through sub-optimal nutrition support.
  • Triathlon Nutrition: Calories, Carbs, Fats, and Proteins - part 1 | EP#94
• According to the ISSN position statement on body composition:
  • There are a wide range of dietary approaches, from low fat to low carb and all points in between that can be similarly effective for improving body composition.
  • Usually, if you control for protein you can achieve great body composition, regardless of how many carbs or fats you take in.
  • Triathlon Nutrition: Calories, Carbs, Fats, and Proteins - part 2 | EP#95
• Don't think you need to go on a named or labelled diet.
• At this point, the collective body of evidence does not suggest intermittent fasting has any advantage over having a normal daily caloric deficit targets for improving body composition.

17:17 - 

• You want to maximise loss of body fat while preserving lean muscle mass, and your health.
• You need a slight energy deficit to achieve a gradual weight loss.
• To maintain lean muscle mass you will need to increase your protein intake.
  • Even if you don't train that much, you will need to go way above the normal recommendations.
  • Go to at least 2g/kg of body weight per day.
    • E.g. If you weigh 70kg, you want to take in at least 140g of protein per day in your energy/calorie deficit stage of weight loss to retain muscle mass.
• A healthy weight loss rate is losing less than 1% of your body weight per week.
  • E.g. if you weight 70kg, you can lose 0.7kg per week while retaining lean muscle mass.
• The higher your baseline weight, the more aggressive you can be in your caloric deficit.
• The ISSN position statement suggests protein intake should increase to 2.3-3.1g/kg of fat-free mass per day.
  • However this may not be significantly different from 2g/kg as this is fat-free mass and not total body mass.
  • Some research in strength training suggests going above 3g/kg.
• Protein intake increase is helpful to retain lean muscle mass because amino acids in protein are the building blocks for muscle.
  • Also, protein has a much higher thermic effect, compared to carbs or fats, which is the amount of energy the body uses to digest and process food.
  • As much as 30-45% of the energy intake from protein goes directly to processing it.
    • For carbs this is 5-15%, for fats up to 5%.
  • Protein is also satiating so it helps you stay fuller for longer, even while in a caloric deficit.
• Regarding the energy deficit, 250-500 kilocalories per day can be an appropriate energy deficit.
  • This will depend on your size, how much energy you expend and how much you usually take in.
  • If you are a female and you're not training much and you usually eat 1500 calories per day, 500 calories a day deficit would reduce your energy availability by too much.
• Regarding the timeline, 3-6 weeks is an appropriate period to achieve your racing weight goals.
  • This also gives you a guide for how much weight you can gain in the off-season.
    • E.g. If your off-season weight is 70kg and you can lose 0.7kg per week, you could cut 4.2kg in 6 weeks.
    • If your race weight is 66kg, you know that in the off-season you shouldn't let yourself go above 70kg.
    • It's recommended to gain weight in the off season, but you might just need to keep an eye on how much you gain.
• The timing of your meals is very important.
  • When you're in a weight loss phase and you do a workout you'd usually consume energy for, you want to continue to do so.
  • You should also continue to consume your post workout nutrition.
  • You could be cutting out calories later in the day.
    • E.g. If you workout in the morning you would have a normal breakfast, a sports drink during the exercise. Then maybe a slightly smaller lunch than normal, and a slightly smaller dinner to get to the calorie deficit for the day.
• Try to consume the kind of food that is satiating.
  • You could eat a large volume of food that is low in caloric density - i.e. vegetables.
• To summarise:
  • Loose your weight slowly - less than 1% of your body weight per week, over a 6-week period.
    • This allows you to preserve lean muscle mass.
  • Increase your protein intake to at least 2g/kg per day or higher.
    • As a consequence you will need to reduce your carb and fat intake.
  • Don't go on any sort of labelled or named diet, or intermittent fasting.
    • They don't give you advantages and may give you additional disadvantages
• Stock your fridge with healthy food options at all times.
  • Make it things that are easy to eat on-the-go - e.g. carrots.
  • Make routines and habits for yourself as this means you won't need to rely on willpower.
• Set up your eating environment to support your goals.
  • E.g. bring a lunch box of healthy food to work.
• Keep your diet quality high.

28:14 - 

• One of the interesting studies I found was called 'Reference values for body composition and anthropometric measurements in athletes', written by Santos and colleagues in 2014.
• They studied hundreds of elite athletes from 21 different sports and most of them (142 females, 339 males) underwent DEXA scans.
• I wanted to suggest some ceilings based on this research. It's not necessarily something to aim for as they were elite level athletes but it can give you a guide as a reference:
  • Median weight, height and BMI:
    • For female triathletes it was 58kg, 168cm and a BMI of 20.4.
    • For male triathletes it was 66kg, 176cm and a BMI of 21.3.
  • Median body fat percentage:
    • For female triathletes it was 20% body fat. (DEXA scans generally come up higher compared to other measurements)
    • For male triathletes it was 11.9% body fat.
  • Median fat free mass index*:
    • For female triathletes it was 16.1.
    • For male triathletes it was 18.5.
• *Fat free mass index is like your BMI, but specifically with your fat-free mass.
  • The highest possible index without using doping is 25. This would come from body building and strength training.

33:17 - 

• Make sure that you understand the limitations of body composition measurement techniques.
• Use the same measurement technique, in the same way, each time.
• Make sure you are aware of the risks involved with losing weight quickly. It's not just impaired training and race performance, it impacts your health too.
  • There is a high prevalence of disordered eating in endurance sports.
  • Extreme behaviour around nutrition and body composition can lead to chronically low energy availability.
• Don't make this too important, it's just one part of the puzzle.

35:00 - 

• The case study is about Hilary Stellingworth, who was a 1500m Olympic track runner twice, in 2008 and 2012.
• The case study was published by Trent Stellingworth (Hilary's husband) in 2017 in the International Journal of Sport and Exercise Metabolism.
  • Trent Stellingworth is one of the top researchers in sports nutrition.
• Over Hilary's entire 9 year career, they used skin fold measurements in 8 locations to estimate fat percentage.
  • Each time that they measured, they added the sum of the skin folds together, and this is what they measured and tracked over her career.
    • It's called the 'sum of 8' skin fold measurement.
• There is a chart of these measurements in the article that is an almost perfect wave formation.
  • Hilary systematically let her weight and body fat increase in the off-season, and then brought it back down for competition.
  • The fluctuations in weight and body fat were 2-4% in each cycle.
• In Hilary's entire career, she only had two injuries that caused her to miss at least a week of training.
  • That is remarkable in the world of track and field.
• Hilary also had above normal bone density (shown through DEXA scans), she had a normal menstrual cycle and her iron levels were great.
  • For an elite endurance athlete, she was very healthy.
• She managed to qualify for the Olympics twice, and also got to the final in the most doped year of athletics ever.
• Hilary was very consistent season to season - she ran 4:05 or below in almost all her years, except when she was pregnant or returning from pregnancy.
• Between the different phases, her average bodyweight fluctuated from 47.2 to 48.3kg in competition versus non-competition phases.
• For the sum of 8 skin folds, it varied from 53.6 versus 61.6mm in competition versus non-competition phases.
• They also found significant correlations in decreasing sum of 8 skin folds during competition periods over her career.
• They found significant positive correlations between slower 1500m race times and increasing sum of 8 skin fold measurements.
  • These correlations were also found for estimated fat mass and actual body weight.
• The takeaway messages from the author of the case study:
  • During non-competition phases they focused heavily on energy availability.
    • Related listening: Triathlon Nutrition: Calories, Carbs, Fats, and Proteins - part 1 | EP#94
  • When they wanted to reach racing weight, they had a 6-8 week period in which they aimed for a daily caloric deficit of 300 calories.
    • She's a light female but she's training a lot, so 300 calories isn't a big deficit as it might be for someone not training a lot.
  • They used various feedback metrics to guide the process of getting to race weight - body weight, but also performance and hunger.
  • The caloric deficit was achieved by cutting back on sweets and fat.
    • They also periodised Hilary's nutrition on a micro-scale, which was done on a day-to-day basis.
    • They made sure she had enough fuel on hard workout days, but cut back on snacks and carbs on easier days.
  • To avoid losing muscle during the weight loss phase they increased her protein to between 2-2.5g/kg bodyweight.
• It can be beneficial to periodise your body composition because it's difficult to maintain your racing weight all year round.
  • You wouldn't try and be in peak shape all year round so don't do it with body composition!
• Although a case study is a very different kind of evidence compared to the joint position statement and the ISSN position statement, it provides a useful example on the topic.
  • I picked this case study because it's a great, well-known researcher who is top of his field.

Links and resources mentioned

• Triathlon Nutrition: Calories, Carbs, Fats, and Proteins - part 1 | EP#94
• Triathlon Nutrition: Calories, Carbs, Fats, and Proteins - part 2 | EP#95
• Nutrition before, during and after workouts | EP#100
• Race-day fueling and The Core Diet with Jesse Kropelnicki | EP#40
• Nutrition and Athletic Performance: Position statement
• Reference Values for Body Composition and Anthropometric Measurements in Athletes
• International society of sports nutrition position stand: diets and body composition
• Case-Study: Body Composition Periodization in an Olympic-Level Female Middle-Distance Runner Over a 9-Year Career.
• How an Olympic Runner Hits Race Weight
• Are athletes winning the war on cramp?

Connect with host Mikael Eriksson

Hi! I'm your host Mikael,

I am a full-time triathlon coach and an ambitious age-group triathlete. My goal is podium at the Finnish national championships within the next few years.

I first started the website Scientific Triathlon in autumn 2015 as a passion project to share my learnings with a larger triathlon audience. Later on, in early 2017 I started the podcast That Triathlon Show. 

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