[Fasting and physical endurance capacity]. / Fasten und Dauerleistungsfähigkeit.

Fasting, or zero calorie diets are used not only by overweight people as a means of losing weight, but by athletes too. Their use is then explained on philosophical grounds, with the aim of even enhancing sports performance. The purpose of this investigation consisted of quantifying the effects of a 10-day fast on maximum performance capacity and endurance (as measured on a bicycle ergometer) of 12 female students of physical education of normal weight. The measurements included resting and exercise metabolism determinants, as well as weight and lean body mass. The main results show that after the diet period the maximum ergometric performance was lower in absolute terms as well as in relation to weight or lean body mass. Performance capacity for submaximal exercise was also reduced. Fat combustion was enhanced both at rest and during exercise. The reduction of maximum performance and endurance capacity may be explained by an enhanced muscle breakdown, an efficiency drop of muscular work, and an inadequate glycogen content of the acting muscles. Shorter fasting periods of 24-36 hours also lead to a lower performance level for exercise bouts extending from several minutes to 1-3 hours. An enhancement of fat combustion was always conspicuous. One may conclude that optimal physical performance is dependent on full hepatic and muscle glycogen stores. Glycogen concentration in the liver decreases sharply as a matter of fact after merely one day of carbohydrate shortage. Zero calorie or low carbohydrate diets are thus at variance with an optimal physical work capacity.

[Possibilities of calculating the fat-free body mass and its reaction to a carbohydrate-poor, fat-rich diet]. / Berechnungsmöglichkeiten der fettfreien Körpermasse und deren Verhalten bei einer kohlenhydratarmen, fettreichen Diät.

9 healthy medical students got an isocaloric fat-rich carbohydrate-reduced diet during 14 days. Body-weight and lean body mass were registrated. We calculated lean body mass from measurement of skinfold thickness, total body potassium and total body water. Body-weight was reduced highly significantly by 3.4 kg on an average. Body potassium and body water remained unchanged. It can be concluded from these results that weight loss was caused by an exclusive reduction of the fat mass.

[Carbohydrate-reduced diet and metabolism: about the influence of a 4-weeks isocaloric fat-rich, carbohydrate-reduced diet on body weight and metabolism (author's transl)]. / Kohlenhydratarme Diät und Metabolismus Uber das Verhalten von Körpergewicht und Stoffwechsel bei einer 4wöchigen isokalorischen fettreichen kohlenhydratreduzierten Kost.

The influence of a 4-weeks carbohydrate-reduced, fat-rich diet on 9 slightly overweighted men was investigated. Caloric and protein intake remained unchanged. 70% were fat, 20% carbohydrates. Glucose, cholesterol, triglycerids, serumproteins, urea, uric acid, sodium and potassium were measured in rest. At a 60 minutes bicycle ergometer test glucose, triglycerids, free fatty acids and glycerol were registrated before and after 20 and 60 minutes work. The intensity was 70% of the maximal oxygen uptake. These were the most important results: (1) Body weight decreased continuously. One of the causes is an elevated heat production. (2) Serum-protein and -glucose remained unchanged. Cholesterol and triglycerides were reduced. Serum-urea, -sodium and -potassium diminished continually. On the contrary, uric acid raised over the normal range. (3) Work performance was reduced for 20%. (4) Hypoglycemic values did not appear. The oxidation of fat by the working muscles, and fat mobilisation increased by a fat-rich diet.