Fat metabolism training
Question:
In the past few months I have only been able to do a little sport. As a result, I got down to 30 per cent body fat. Now I want to get back to my ideal weight. How should I train?
Answer from Dr Merkl:
Body fat is the largest energy store for endurance athletes: One kilogramme of fat yields around 7,000 kilocalories and thus mathematically provides energy for eight to ten hours of cycling. However, fat only fulfils its function as an energy store if its proportion is as low as possible compared to the active fat-free body mass. Top trained female athletes have around ten per cent body fat, athletes around five. Casual sportswomen should have no more than 25 per cent, casual sportsmen no more than 20 per cent. Reducing the fat percentage increases the performance of the fat-free active body mass because the lost fat no longer needs to be supplied by the metabolism - the body can absorb more oxygen and the muscles are relieved. Cyclists who want to lose weight must make sure that they actually obtain the energy they need from fat. As a general rule, fat loss is less or even non-existent if the pace is too high. If you want to lose fat, you need to keep your exertion level low (apart from top athletes, the body only utilises fat reserves at around half the maximum exertion level). If you want to improve your fat metabolism, you should therefore train at a low level of exertion and choose a long duration of exertion of at least 30 to 40 minutes, as fat can only be integrated into the metabolism to a high degree after 30 minutes. As a rule of thumb, you should only cycle at a speed where you can still hold a conversation and your heart rate is no higher than around 180 minus your age.
Weight reduction through ergometer training
Question:
I train five times a week for 50 minutes on the ergometer with the aim of losing weight. I keep reading that fat burning is best when the heart rate is 60 to 70 per cent of the maximum heart rate. I strictly adhere to this, but the desired effect has not yet materialised. Why is that?
Answer from Dr Merkl:
During a 50-minute workout at around 60 per cent of maximum oxygen consumption, energy stores in the muscle and glycogen from the liver are converted at the beginning. Only after 15 to 20 minutes has the fat metabolism got going to the extent that 50 per cent of the energy burnt comes from fats. This proportion increases to around 80 per cent after a total of 30 minutes. Assuming a calorie consumption of 600 calories per hour, a maximum of 250 calories of fat can be burned during a 50-minute ergometer workout. If you know that one kilogramme of fat stores the energy of around 7,000 calories, it is therefore not surprising that your ergometer training has not yet resulted in any noticeable weight loss. In addition to extending your training sessions to over an hour, you will probably have no choice but to reduce your food intake.
Fat metabolism/adjustment after exercise?
Question:
Does the body switch from carbohydrate to fat metabolism after the ascent, before which I was travelling in the basic range (fat burning), or are the carbohydrate reserves then completely used up?
Answer from Dr Merkl:
During long training rides, the body provides a large proportion of its energy via fat metabolism. However, the body's energy supply is always mixed: the body does not obtain its energy solely from fat in the basic range, nor does energy come exclusively from carbohydrates during intensive rides. If you are well trained, the proportion of energy production from fat is particularly high: this means that it starts very early and a very high proportion of maximum performance can be achieved with its help. If you have good basic endurance, your carbohydrate stores will be spared even on a mountain run and you will still be able to cover a long distance in the basic range afterwards.
Fasting
Question:
Next year I wanted to do two to three weeks of fasting, each with five fasting days. Does fasting between training phases have a negative effect on the body?
Answer from Dr Merkl:
Health fasting with a zero-calorie diet, especially in combination with sport, is extremely controversial in medicine. Instead, I would recommend a gentle diet in which your food intake is no more than 1,000 calories below your daily requirement. Cutting back in this way will result in a weight reduction of around one kilo in six days. To control your energy intake, you need a calorie table from the pharmacy. When reducing calories in combination with sport, carbohydrates should be the most important source of energy and their proportion of the total diet should increase as you reduce your weight. Cereal products, potatoes, rice and fruit should be the preferred sources. You can get vitamins and minerals from fruit and steamed vegetables. Also make sure you drink plenty of fluids.
