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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. On the flat, this is reduced.
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; this would be 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 weight for weight, fat yields the most energy. 1g of carbohydrate provides 3.75kcal, and 1g of fat provides approximately 9kcal. 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 6½ kg of cooked quinoa.
When we train, especially hard training, we use more carbohydrates, and if we do not have the necessary carbs, 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 that 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. A major reason for this is that 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 muscle loss.
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, but they can provide a guide for weight loss and the monitoring of that weight loss.
Nigel Mitchell is Technical Lead for the English Institute of Sport, nutritionist for British Sailing and an honorary senior lecturer at the University of Portsmouth.Find out more about Healthspan's Expert Panel.
Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn’t possible supplements can help. This article isn’t intended to replace
medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.