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Dietary Considerations for Cutting Weight as an Athlete

If you are an athlete your goal is to train, recover, adapt and perform to your potential. And by ‘athlete’ I mean anyone from a recreational weekend warrior who cares about their performance through to an elite international champion.

When cutting weight* as an athlete there are two primary potential ‘problems’:

  • The problem of energy: Athletes need energy to train, recover, adapt and perform to their potential. Cutting weight requires energy (calories) intake < energy (calories) burned. How do athletes cut energy intake, without compromising training, recovery, adaptation or performance?

  • The problem of muscle: Athletes want to cut body fat and preserve (or even build) their muscle weight**. As these muscles are critical to performance. How do athletes maximise fat loss and minimise muscle loss when cutting weight, i.e. how do athletes make weight loss selective for fat loss?

*I am talking about cutting weight with the idea of keeping it off long term, rather than temporary losses such as to make a competition weight class through short term low residue diets and other strategies.

**Okay okay, there are some exceptions. If you are a bodybuilder who wants to become an endurance runner that upper body muscle is pretty much dead weight to you now. But as a general rule, we want to lose fat and preserve muscle!

In this article, we look at components of nutrition (energy in) relevant to both these parts of the ‘problem’. As will be highlighted, any one component might be more or less relevant to any one athlete, dependent on factors including: 1) What their sport is, 2) The nature, volume and intensity of their training, 3) Their current general and sport specific fitness, and 4) Their current and target body fat percentage. References and links to read more are provided for those who want to take a deep dive into any of the areas, and more … this article is a whistlestop tour to introduce you to the things to consider.

Size of the calorie deficit

The laws of physics cannot be out manoeuvred: to lose mass energy (calories) in must be less than energy (calories) out. But how big should that deficit be? For athletes, the short answer appears to be “As small as possible to achieve your goals”. Why? …

Low Energy Availability is Not Good!

The body cannot run on empty. We need energy to maintain every part of our body – from our skeleton to our immune system to our reproductive system. If energy intake is too low, as well as short and long term sports performance, these systems start to break down. And for some systems, this damage is hard to reverse. For example, bone mineral density lost from the skeleton may never recover, which increases the risk of osteoporosis and potentially limits an athlete’s involvement in their sport. Such health damaging impacts are estimated to occur when we eat less than 30kcal per kg fat free mass in the body, when at rest (See review by Melin et al 2019). Short term periods of 30-40kcal per kg fat free mass at rest are estimated to provide a rate of weight loss that – at least when undertaken for short periods – are not expected to lead to the adverse health outcomes of low energy availability (See review by Melin et al 2019). It is important to note this is AT REST i.e. calories must also be consumed above this to account for those burned in training.

It is worth noting that when we eat in a calorie deficit, particularly for long periods and with significant weight loss, we appear to undergo metabolic adaptation (adaptive thermogenesis). This is where the body appears to conserves energy, reducing energy output and therefore the size of the calorie deficit. As we lose weight be burn fewer calories as we simply have less weight burning calories and less weight to carry around, however it seems that the reduction in calories burned (energy out) may be 10-15% higher than is explained by the amount of weight lost (See Aragon et al 2017). Some of this may be due to a reduction in things like fidgeting, and some may be due to the reduced functioning of certain systems in the body – as we see with low energy availability.

If Our Goal is to Preserve Lean Mass

The more aggressive the calorie deficit and rate of weight loss, the less this is made up of fat loss and the more it is made up of lean mass. Perhaps in part because of reduce synthesis of lean tissue such as muscle (Pasiakos et al 2013). Studies in overweight and obese populations suggest lean mass may account for up to 25% of the weight lost on very low calorie diets (See Saris 2001). And the leaner you are and the more lean mass you have, the greater the proportion of the weight lost is expected to be lost as lean mass. As such, a slower rate of weight loss is expected to better preserve lean mass. At least in resistance trained populations it is suggested that a rate of weight loss of 0.5-1.0% per week may be optimal (Helms, Aragon and Fitschen, 2014).

It is interesting to note that a study of elite gymnasts and runners found that the greater the calorie deficits the athletes had in a day, the higher their body fat percentage (Deutz et al 2000). However, it is not clear whether this was because of loss of lean mass in those with higher calorie deficits, or because the athletes with higher body fat percentages were dieting to reduce body fat.

In sedentary overweight populations, taking up resistance training concurrent with cutting calories has been shown to preserve lean mass (Donnelly et al 1993; Longland et al 2016; Hector et al 2018). However, it is not clear whether the same would be seen in athletic and trained populations – particularly those that already resistance train (Demling and De Santi 2000).

Of course, loss of lean mass is not a direct indicator of loss of performance, but it is an indicator that performance – or performance improvements – may be compromised if muscle mass required to generate the energy, power and speed of your sport is lost. In this regard, one study looked at changes in strength with 0.5kg versus 1.0kg loss of bodyweight per week in active non-athlete females (Mero et al 2010). There was a significantly greater loss of strength in the 1.0kg per week group. However, jump height performance improved significantly in the 1.0kg group likely because the individuals were lighter. As such, perhaps the importance of preserving lean mass – at least in the short term – may to a degree be dependent on your sport!

Macronutrient Split

The calories we eat are made up of the three macronutrients of protein, fats, and carbohydrates. Total calories are the primary determinant of bodyweight, however how does the split of macronutrients within this contribute to body composition and performance when cutting weight?

Protein intake over and above that required when we are not in a calorie deficit appears to be important in preserving muscle mass, at least in resistance trained / resistance training individuals. Research suggests an intake between 2.3-3.1g of protein per kg of bodyweight may be optimal (Celejowa and Homa 1970; Maetsu et al 2010; Mettler, Mitchell and Tipton 2010; Helms et al 2013; Campbell et al 2018). It has been hypothesised that highly resistance trained individuals with high lean mass may need to err towards to the higher end of the range for maximal preservation, as they are expected to be more efficient at using protein (see Helms et al 2014). It seems likely that the increased protein is required to support maximal muscle protein synthesis, which may be suppressed in a calorie deficit (Pasiakos et al 2013) and potentially to mitigate against the use of muscle protein to provide energy in times of shortage.

Of course, the greater the proportion of total calories used to consume protein, the less available for consumption of carbohydrates and fats. We know that carbohydrates are important for performance in sports above low to moderate intensity, and that carbohydrate demand of an athlete depends on the amount of ‘work’ (training) they are performing – both in terms of duration and intensity (see Burke et al 2011; Hawley 2015). As such, whilst total intake may be compromised, for optimal performance athletes may consider following as closely as possible the guidelines provided by Burke et al (2011), in particular during and after intense training sessions.

This leaves fats. From a performance perspective, the impact of altering fat intake (without impacting carbohydrate or protein intake) is not clear. It is only the primary fuel for lower intensity exercise and can be liberated from internal fat stores, although as these deplete as individuals become leaner this becomes more challenging. However, fat is essential to life and health! A general recommendation is that fats should form at least 20% of total caloric intake in athletes, although there is likely to be a cap and floor on this dependent on total calorie intake.


By this we mean when food is eaten, with respect time of day and time of training. Very few studies have looked at the impact of nutrient timing on performance when in a calorie deficit, and so I refer you to broader consideration on nutrient timing for athletes in my blog here. We can speculate that optimal timing of protein intake, particularly before bed, and maximising the window of fastest carbohydrate refuelling post training may be of increased importance when cutting weight. The logic for this being that we have fewer ‘spare’ calories / macronutrients lurking around and so we need to be as efficient as possible in using the ones we do have for refuelling our muscle carbohydrate stores, and repairing and building our muscle protein for performance. But this is speculative – the studies need to be performed to investigate it!

Interestingly, one study has compared time restricted feeding (intermittent fasting) with feeding across a whole day on body composition and strength performance in resistance trained individuals (Moro et al 2016). Total calories and macronutrients consumed across the two groups was equivalent, and they were in a calorie deficit. The timing of the meals in the time restricted group was centred around the time of day when the individual’s resistance trained. Interestingly, the time restricted feeding group lost more fat mass, although strength was unchanged between the groups. Considering that in sedentary populations there appears to be no difference in rates of weight loss between intermittent fasting and continuous eating when calories are matched (La Bounty et al 2011; Kerksick et al 2017; Sundfor et al 2018), it is interesting to speculate whether the time restricted group could utilise their food intake more effectively, storing less as fat, because of having more of their calories available around their training. However, multiple other explanations are equally plausible. Further studies are needed!

What foods

Fewer calories = fewer opportunities to get in all the fibre, vitamins, minerals, and other goodies you need from food (Loosli and Benson 1990). These are vital for long term health and performance. So, when cutting weight, we are likely going to need to focus on getting the biggest bang for our buck in terms of the foods we choose. This might mean not reaching for your protein or carbohydrate powder so quickly … these provide the macronutrients, but often little in the way of micronutrients and fibre.

In addition, there is some evidence that whole foods are more satiating than processed foods containing refined ingredients (Holt et al 1995), and that we use more energy digesting whole foods than we do processed foods (Barr and Wright 2010), thereby increasing our energy out and therefore the size of the calorie deficit.

Summary …

So, in conclusion the evidence suggests:

  • Eat as much as possible to get to your weight cut goals, which translates to at least 30kcal per kg of fat free mass per day and potentially a rate of weight loss that does not exceed 1.0% of bodyweight per week;

  • Consider high protein intake, carbohydrates to match your activity levels, and fat of at least 20% of calories;

  • Eat sufficient protein regularly, including before bed, and time carbohydrate intake around training; and

  • Focus on whole unprocessed foods, rich in vitamins, minerals and other micronutrients.


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