Some effects of an excess intake of carbohydrate on man and rats

Abstract

1. In 19 experiments of short duration (arranged in 3 series) it was found difficult to raise the R.Q. in man above 1.0 after an excess intake of carbohydrate.

2. In Series 1, 8 subjects received 4 meals supplying a total of 399 -505 g. carbohydrate and the maximum mean R.Q. was 0.94 in a 14 h. period.

3. In Series 2, 9 men received 597-1172g. carbohydrate in 5 meals. During 24 h. a maximum mean R.Q. of 0.99 was reached at 2.0 a.m. The full water balance was determined.

4. The period of study was extended to 8 days in Series 3 when the effect of a mid-day meal rich in carbohydrate was followed for 6h. each day, with 2 subjects. The meal was superimposed on a normal diet for 2 days, a diet low in fat for 4 days and a diet containing excess carbohydrate for 2 days. Even on the final day the net conversion of carbohydrate to fat was negligible.

5. The effects of overeating for a longer period were investigated with 2 overweight women while in hospital for 23 days. After 9 days on a control diet, they received an excess intake for 9 days and were underfed for 5 days. During the overfeeding period they received 7290 and 10440 kcal in excess of their energy expenditure and gained respectively 2.86 and 2.58 kg. in 9 days. During the 5 days of underfeeding they lost 6.22 and 5.63 kg. with a negative calorie balance of 12100 and 13850 kcal. respectively. The changes in body composition for each period were calculated.

6. The interpretation of R.Q.'s and their validity as an index of the metabolic mixture, is discussed.

7. The slow rise in the R.Q. and the small net conversion of carbohydrate to fat in these experiments suggests a temporary storage of carbohydrate before its conversion to fat. This hypothesis was tested by an experiment with rats. With a mean R.Q. of 0.81 the glycogen content of rat muscle was 0.29% while with an R.Q. of 1.03 the muscle tissue contained 0.64% glycogen. In both man and rats there appears to be a delay in the net conversion of carbohydrate to fat following an excess intake of carbohydrate.