1290
Letters
the amount of exercise are common in everyday life and these results indicate a mechanism involved in the control of energy output tending to regulate energy balance. Nutrition Department, D. S. MILLER Queen Elizabeth College, A. WISE. London W8.
the Editor
to
EXERCISE AND DIETARY-INDUCED THERMOGENESIS
SIR,—While conducting his experiments on metabolism in the late 18th century, Lavoisier observed that food intake in a warm environment increased the rate of oxygen consumption in man. This phenomenon, dietary-induced thermogenesis (D.I.T.), could be part of a mechanism whereby energy output is controlled. It is possible that the quantity of D.l.T. could reflect the previous diet as a whole, but this aspect has received little attention. D.l.T. is very variable while exercising, and in order to emphasise this condition, we have interpreted the literature and expressed our experimental results in terms of the cost of (kj per min.) (FIGURES DUPLICATES)
COST OF EXERCISE AFTER BREAKFAST MEANS OF
ARE
exercise. Several authors found that the cost of exercise was greater after a meal than before,1-4 and others showed that the cost of exercise was unaffected by a meal 5-8 ; others showed that the
cost
of exercise
lower after a of exercise but decreased in
was
meal,9,"O and another 11 found that the
cost
after a meal increased in one subject another. In order to show whether these confusing results could be due to the previous dietary status of the subjects, the
following experiment
was
designed.
A pulley mechanism was arranged so that human volunteers lifted weights of either 3,3 kg. or 0,3 kg. vertically (75 cm.) by means of horizontal arm movements. The cost of lifting 3-0 kg. was calculated by difference. _For one day previous to the test the subject ate either 4, 10, or 17 MJ diets; these diets were made up in such a way that the proportions of nutrients approximated those normal in a British diet. The energy required to lift 3-0 kg. was measured before breakfast and 6 times during the three hours following breakfast; the breakfast contained 3-9 MJ made up of 44% fat, 42% carbohydrate, and 14% protein. Four subjects each performed the experiment in duplicate. The cost of exercise before the meal was unaffected by the previous diet; the cost of lifting 3-0 kg. after eating 4, 10, or 17 MJ diets was 2-8, 2-4, and 2-6 kJ per min., respectively. But after the meal the cost of exercise depended on the intake of the previous day (P
Letters
the amount of exercise are common in everyday life and these results indicate a mechanism involved in the control of energy output tending to regulate energy balance. Nutrition Department, D. S. MILLER Queen Elizabeth College, A. WISE. London W8.
the Editor
to
EXERCISE AND DIETARY-INDUCED THERMOGENESIS
SIR,—While conducting his experiments on metabolism in the late 18th century, Lavoisier observed that food intake in a warm environment increased the rate of oxygen consumption in man. This phenomenon, dietary-induced thermogenesis (D.I.T.), could be part of a mechanism whereby energy output is controlled. It is possible that the quantity of D.l.T. could reflect the previous diet as a whole, but this aspect has received little attention. D.l.T. is very variable while exercising, and in order to emphasise this condition, we have interpreted the literature and expressed our experimental results in terms of the cost of (kj per min.) (FIGURES DUPLICATES)
COST OF EXERCISE AFTER BREAKFAST MEANS OF
ARE
exercise. Several authors found that the cost of exercise was greater after a meal than before,1-4 and others showed that the cost of exercise was unaffected by a meal 5-8 ; others showed that the
cost
of exercise
lower after a of exercise but decreased in
was
meal,9,"O and another 11 found that the
cost
after a meal increased in one subject another. In order to show whether these confusing results could be due to the previous dietary status of the subjects, the
following experiment
was
designed.
A pulley mechanism was arranged so that human volunteers lifted weights of either 3,3 kg. or 0,3 kg. vertically (75 cm.) by means of horizontal arm movements. The cost of lifting 3-0 kg. was calculated by difference. _For one day previous to the test the subject ate either 4, 10, or 17 MJ diets; these diets were made up in such a way that the proportions of nutrients approximated those normal in a British diet. The energy required to lift 3-0 kg. was measured before breakfast and 6 times during the three hours following breakfast; the breakfast contained 3-9 MJ made up of 44% fat, 42% carbohydrate, and 14% protein. Four subjects each performed the experiment in duplicate. The cost of exercise before the meal was unaffected by the previous diet; the cost of lifting 3-0 kg. after eating 4, 10, or 17 MJ diets was 2-8, 2-4, and 2-6 kJ per min., respectively. But after the meal the cost of exercise depended on the intake of the previous day (P
