How do I lose weight but not compromise training?

Weight management is a topic that competitive endurance athletes love to discuss. The issue is how do you reduce your calorific intake enough to lose weight but ensure you have adequate energy for training?

In endurance sport, carrying extra weight slows you down. On the bike when climbing on a 6% climb, 1kg is equivalent to having to produce about an extra 6 watts of power.

To understand this we need to examine and challenge some of the basic principles of nutrition. In very simple terms the body stores all extra energy in the form of adipose (fat). We store a small amount of energy in carbohydrate, in the region of 60g, in the liver and a few hundred grams in lean tissue.  Even in a lean person, the body likes to store about 10kg of fat and the reason we store all of this excess energy as fat is because pound for pound, fat yields the most energy. 1g of carbohydrate provides 3.75kcal and 1g of fat provides approximately 9kcal per gram. Body fat (adipose) is not pure fat, so 1g of adipose is approximately 7kcal.  That means 1kg of adipose is worth about 7000 kcal. Therefore to lose 1kg of body fat you need to be in an energy deficit of 7000 kcal. In exercise terms that is equivalent to someone running about 70 miles, or in food terms this is equivalent to about 28 big Macs or about 6.5 kg of cooked quinoa.

When we train, we use more carbohydrates and if we do not have it, it will affect the quality of training.  We have all under-fuelled and felt the results of ‘bonking’.

One other point we must consider is when we are losing weight we want to lose fat not muscle, however all too often when we reduce energy intake we lose both fat and muscle. There are many reasons for this but one major reason is when we reduce energy, especially from carbohydrate, the body will use more protein. There are both dietary and exercise strategies that can reduce and prevent the loss of muscle.

Before starting a weight loss plan, people should consider whether it is worth the additional work and stress. Also, how much weight have you got to lose?  Today there are many body composition monitoring devices, such as scales that use bio impedance to gauge body composition.  The precision of these can be variable however they can provide a guide for weight loss and also the monitoring of weight loss.

Below are the key points for effective weight management:

  • How much is the desired weight loss?
  • Following a weight reducing diet can add additional stress to the body. Only start this if you have good health.
  • It is a good idea to have iron stores checked and if low, consider an iron supplement.
  • Plan gradual weight loss. This will compromise training and recovery less than rapid weight loss. 500g -1kg a week is about the maximum you should aim for; this is a deficit of 500-1000 kcal per day.
  • Try to plan the weight loss at times when you do not have intense training.
  • Ensure that you have about 1.5-2g of protein per kg of body weight a day. This should be split up throughout the meals. g. a 70kg triathlete would require about 100 -140g of protein a day.  Dairy protein is particularly good.  However if someone is vegetarian or vegan this should not be a problem. There are plenty of good vegetarian sources of protein. Foods such as quinoa, soya, pulses and nuts are particularly good vegetarian proteins.
  • Periodise your carbohydrate intake. If you are doing light or low intensity training, reduce the carbohydrate around the training session. If the following day you have a hard session, then carbohydrate should be increased after training.
  • Quick and slow carbohydrates. Base your carbohydrates mainly on low glycemic index (GI) foods such as porridge, sweet potatoes, and quinoa. These carbohydrates are more slowly absorbed.
  • Include a mid morning and mid afternoon snack. I find something like a banana or about 40g of pistachio nuts work well.
  • Healthy fats. A common mistake is for people to cut fat back too far. Like proteins, we have essential fats as well.  I always recommend that when people are on a weight loss plan that they include fats such as oily fish, eggs, avocado, milled seeds (see seed and berry mix recipe), pistachio nuts, olive oil.  I would normally recommend an omega three supplement high in Eicosapentanoic acid (EPA) aiming for about 1-2g a day.  Also with elite athletes I may include a CLA supplement as well.
  • Monitor your weight. Try to get weighed on the same scales at the same time each week and keep a record of this.
  • Resistance work, some strength work will help to reduce muscle loss.

For most triathletes weight management should not be a big issue, and for anyone who is really unsure they would benefit from some professional dietary input.  The SENr register provides a list of suitable qualified sports nutritionists.


Nigel Mitchell is a Healthspan Elite expert nutritionist. Healthspan Elite supplements have been the secret of professional athletes, used by everyone from international rugby teams and Premier League football clubs to Olympic gold medallists and Tour de France winners. Developed alongside leading nutrition and sports experts, Healthspan Elite provides a comprehensive range to meet your nutrition needs. For information on the full range go to