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Beyond ‘Eat Less, Move More’: The Art and Science of Cutting Weight and Performance

So you want to cut weight. Maybe this is to compete in a lower weight class, to move faster, for aesthetics, or to lean before a strength and gain cycle. Whatever the reason, you face a common challenge: how to give your body the fuel it needs to train, recover and perform to its best in your chosen sport, whilst still creating a calorie deficit.

A calorie deficit = calories eaten are less than calories burned

The laws of physics cannot be out manoeuvred, this is the only way to lose body mass. As can be seen by the equation, there are two ways to create a calorie deficit: reduce calories eaten and / or increase calories burned.

Athletes, be they competitive or recreational, are already training hard and so increasing physical activity to significantly increase calories burned may not be possible, practical, or sensible. If this is the case, the calorie deficit must be driven by reducing calories eaten. It turns out that to cut weight most effectively and maintain athletic performance it isn’t quite as simple as just cutting calories any old way. The type of calories eaten, the time they are eaten, and the size of the calorie deficit all play a role. A calorie is not just a calorie.

The types of calorie and when we eat them: Protein, Fats and Carbs

Proteins, carbohydrates and fats (the macronutrients) are the calories we eat. Protein is the fundamental building block of muscle. Carbohydrates provide the fuel for high intensity exercise. Fat is a building block of tissues and hormones, and is required to access fat soluble vitamins and minerals. We need each of these to be healthy and support athletic performance. The question is – how much of each do we need, and what do we cut in a calorie cut?

As always, the answer is ‘it depends’. On your sport, gender and starting physiology.

Protein is not a typical source of fuel source for the body. It is a building block of tissue, and the fundamental building block of muscle fibres. We burn protein as fuel only when in ‘starvation’ mode, when we have exhausted carbohydrate supplies and cannot access our fat stores fast enough (or do not have enough fat) for the energy we are using at any one point in time. In a caloric deficit, we are at risk of breaking down protein, particularly skeletal muscle protein, to use as fuel as we are essentially in ‘starvation’ mode for one or more hours in the day. Unsurprisingly then, the faster the rate at which an individual loses weight, the greater the contribution of muscle loss to this. Research indicates that when we are not ‘dieting’, between 1.6-2.2g / kg bodyweight per day supports maximal muscle protein synthesis in resistance trained individuals, i.e. those individuals with the greatest protein requirements typically (Schoenfeld et al 2018). However, when hypocaloric as much as 3.4g/kg bodyweight per day may help preserve maximal muscle mass in resistance trained athletes (Schoenfeld et al 2018). Moreover, muscle is the most metabolically active tissue at rest. So apart from for performance and aesthetic reasons, you want to preserve as much of this as possible to maintain a higher calorie burn!

Next up, carbohydrates. The necessary fuel for maximal intensity exercise lasting longer than a minute. Glycogen, the carbohydrate energy store in our body, is used up to provide energy as we exercise at a moderate to high intensity. Unsurprisingly, low muscle and liver glycogen levels adversely impact both the all-out intensity and reduce time to exhaustion at such intensities. As exercise intensity decreases and duration increases, for example extremely long low intensity endurance activity, the proportion of energy provided by carbohydrates decreases and the proportion provided by fat increases. There are an increasing number of advocates for the ketogenic diet for endurance performance and body composition, particularly when in a caloric deficit. The ketogenic diet is high fat, low protein and very low carbohydrate. Proponents argue that such a diet forces adaptations in the body that make it more efficient and better at using fat as fuel. This appears to be true for low intensity exercise. However, research to date has demonstrated the ketogenic diet does not enhance endurance performance, and impairs muscle glycogenolysis and energy flux, thereby limiting high intensity energy production (Hawley and Leckey 2015). As such, severe limitation of carbohydrates to reduce calories is not recommended for individuals whose chosen sports are high intensity. Individuals undertaking such exercise must ensure that even when eating in a caloric deficit they take in sufficient carbohydrates to fill muscle and liver glycogen stores before and after training.

And now, fats! Whilst we don’t want to try and rely on fats for high intensity athletes, fats are essential. Women have essential body fat of 10-12% total mass, athletes typically have body fat of 12-22%, and the generally fit 16-25%. In men these % are lower at 3-5% essential body fat, 5-13% for athletes, and 12-18% for general fitness. For the general population, the recommendation is that fats should comprise 30-35% daily calories. For athletes, because of their protein and carbohydrate requirements, this is reduced to 20-25% (see comment on the ketogenic diet above!). It is not recommended to drop below 20%, as this will risk being unable to obtain sufficient essential fatty acids, fat soluble vitamins and minerals and the substrates to produce the essential steroid hormones – and falls in testosterone are going to be inhibitory to muscle mass gain, and in oestrogen to maintenance of bone density, the menstrual cycle and other immunological functions.

Finally, when choosing foods on a cut it is important to consider how to obtain a complete spectrum of vitamins and minerals because when we reduce the amount of food we are eating, we are at increased risk of micronutrient deficiency: less food = less opportunity to consume vitamins and minerals. And without vitamins and minerals we can struggle to effectively access and use the energy and building blocks our food provides, recover from training, maintain our immune system, function cognitively … basically everything we do as living breathing humans!! One study found that athletes eating in a caloric deficit were deficient across a spectrum of both fat and water soluble vitamins and minerals (Loosli and Benson 1990). To reduce the risk of deficiencies, eat a variety of whole unprocessed foods, focussing on vegetables and fruit that are all colours under the sun, a variety of meat and fish, complex carbs, and fat sources. Yes, it might take some more time to think of and prepare meals … but it could be the difference between being able to train hard and perform over extended periods, and not!

When we eat: Does timing matter?

In athletic populations, the answer appears to be a distinct ‘yes’. Both for appropriate fuelling for the work required, and for effective recovery and strength and performance enhancement. Timing of nutrient intake around training when in a calorie deficit may be particularly important to ‘offset’ the impact of having fewer overall calories for fuel and building tissue across each day.

The critical elements appear to be, first, providing sufficient carbohydrates to maximise muscle and liver glycogen stores before high intensity exercise (particularly that lasting longer than 1 hour), and restore glycogen levels after training. The current recommendations across sporting bodies are, on average, up to 2.5g/kg carbohydrates 2-4 hours before a long high intensity training session, and then 1g/kg carbohydrate within 1 hour of completing training, and a further 1g/kg carbohydrate within the next 2-4 hours.

Research indicates that regular protein intake across the day supports maximal muscle mass preservation and hypertrophy (Phillips et al 2016; Morton et al 2018; Reidy and Rasmussen 2016). This is because, first, muscle protein synthesis remains elevated for 24 hours post training and, second, because the body cannot store amino acids and so must obtain the essential amino acids for muscle protein synthesis ‘fresh’ throughout the day (Phillips et al 2016). On top of this regular intake, consuming 20-40g of a fast digesting protein such as whey immediately post training has been shown to have a further incremental benefit to muscle protein synthesis in multiple studies in both men and women (Macnaughton et al 2016; Schoenfeld et al 2018). It is worth noting that 30-40g casein protein before bed has been shown to increase overnight muscle protein synthesis and resting metabolic rate, and maintain rates of breakdown of stored body fat (Madzima et al 2014). This finding is consistent with findings of other studies in both athletic and non-athletic populations (Jager et al 2017). This suggests a meal of casein before bed has a beneficial impact on body composition, and may be particular relevant to athletes eating in a calorie deficit who may be at increased risk of ‘starvation’ mode and hence muscle protein breakdown for fuel overnight.

I will be putting up a blog discussing nutrient timing more extensively soon – take a look at this when it comes out for further detail!

Size of the deficit: how many calories to cut

Research indicates that a 300-500kcal daily calorie deficit gives the greatest rate of fat loss, relative to calorie deficit, as well as the greatest likelihood of sustained weight loss. Having said this, there is significant individual variability in the optimal caloric deficit. Typically, the more excess fat an individual has, the greater caloric deficit they can typically sustain whilst maintaining an optimal rate of fat loss and good health. As such, a better guide to optimal weight cuts may be from studies looking at % bodyweight drops; studies on natural bodybuilders indicate a drop of 0.5-1% bodyweight per week drives the greatest rate of fat loss: lean mass preservation with the appropriate nutrition and training plan (Helms et al 2014).

Too big a calorie deficit and you will not have sufficient glycogen to power intense training sessions, or the proteins, fats and carbohydrates to recover and undergo effective training adaptations in the form of muscle growth and improved energy systems. This will result in inhibited performance and performance improvement. It will also result in fewer calories burned, thus hindering weight loss itself – and exercise activity can contribute as much as 10-30% of total calories burned per day in active individuals.

In addition, studies have shown that if calories are significantly reduced, the decrease in resting metabolism exceeds that attributable to the loss of body mass and therefore reduced energy required to maintain your body tissue and move your body around (Bray 1969; Lanham et al 2011; McArdle et al 2015). This conserves energy causing the diet to become progressively less effective despite calorie restriction. In our evolutionary history this was eminently sensible and likely a key to survival, when famine or inability to find prey to hunt continued for extended periods. In today’s western society of overabundance this is not so much a concern … but how are our bodies expected to know this when for millennia it was not the case!!

How do our bodies ‘conserve’ energy by reducing our resting metabolism when we cut calories ‘too much’? It appears that we get changes in circulating hormones, mitochondrial efficiency (meaning we produce more energy from less food) and energy expenditure (even as simple as fidgeting less!) that serve to minimise the caloric deficit (Douyon and Steingart 2002; Friedl et al 2000). There is evidence that intermittent refeeding to slightly above maintenance levels, principally on carbohydrates, restores circulating leptin levels and metabolic rate – thus promoting continued weight loss when return to a caloric deficit (Douyon and Steingart 2002; Friedl et al 2000). The long term health implications of such strategies are not yet fully understood.

How do you know if you have gone too far by cutting calories too much? The first indications may be fatigue, trouble sleeping, declining performance in the gym, excessive hunger, frequent illness. The International Olympic Committee defined Relative Energy Deficiency in Sports (RED-S) as a condition that ‘affects many aspects of physiological function including metabolic rate, menstrual function, bone health, immunity, protein synthesis, cardiovascular and psychological health’. At one time this syndrome was focussed on women, however it has now been recognised that it also impacts men.

Round up

Cutting weight and maintaining performance is more than just ‘eat less, move more’! Athletes must consider how they continue to fuel their training to maximise performance. This includes not just the calories to provide energy, but also the building blocks to repair and grow muscle and other tissue, and the micronutrients to do this and maintain good health.

And we must also remember that every body is different. As well as training volume and intensity, and start and desired end bodyweight, your optimal weight cutting strategy will depend on your age, gender, genetics, lifestyle, and psychology. As such, it may take some trial and error and a few tweaks to the general principles until you find what works best for you. And as you drop weight and your body composition changes, your energy requirements will change – meaning you may need to review and adjust your nutrition strategy to remain in an appropriate calorie deficit.


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