Historical Events

Professor Kekwick and Dr Pawan undertake study where they find that obese patients would lose weight so long as the calories consisted chiefly of protein and fat, and the carbohydrates were kept to a minimum.

Calorie intake in relation to body-weight changes in the obese.

https://www.scribd.com/doc/28131415/Kekwick-Pawan-1956-Lancet

https://sci-hub.tw/https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(56)91691-9/fulltext

MANY different types of diet have been successfully used to reduce weight in those considered obese. The principle on which most of them are constructed is to effect a reduction of calorie intake below the theoretical calorie needs of the body. Experience with these patients has suggested, however, that this conception may be too rigid. Many of them state that a very slight departure from the strict diet which can hardly affect calorie intake, results in them failing to lose weight for a time. Though it is realised that evidence from such patients is notoriously inaccurate owing to their approach to this particular condition, it is too constant a belief among them to be entirely discarded. Furthermore, most of the diets in common use not only restrict the intake of calories but also radically alter the proportions provided by protein, fat, and carbohydrate. In this country a healthy sedentary person may be supposed to consume some 2200 calories daily, made up of about 70 g. of protein, 60 g. of fat, and 350 g. of carbohydrate : protein supplies 12% of the calories, fat 24%, and carbohydrate 64%. On most reducing diets, however, the carbohydrate and fat will be restricted while the protein remains about the same ; and in a diet yielding 1000 calories protein may provide 30%, fat 37%, and carbohydrate 33%. Finally, Lyon and Dunlop (1932) observed that patients on isocaloric reducing diets lost weight more rapidly when the largest proportion of the calories was supplied by fat than when it was supplied by carbohydrate. Anderson (1944) attributed these findings to the different amounts of salt (causing water retention) in the diets used by these workers. More recently, Pennington (1951, 1954) has recommended high-fat diets in the treatment of obesity. It therefore seemed important to establish which factor has the greater effectrestriction of calories, or alteration in the proportions of MANY different types of diet have been successfully used to reduce weight in those considered obese. The principle on which most of them are constructed is to effect a reduction of calorie intake below the theoretical calorie needs of the body. Experience with these patients has suggested, however, that this conception may be too rigid. Many of them state that a very slight departure from the strict diet which can hardly affect calorie intake, results in them failing to lose weight for a time. Though it is realised that evidence from such patients is notoriously inaccurate owing to their approach to this particular condition, it is too constant a belief among them to be entirely discarded. Furthermore, most of the diets in common use not only restrict the intake of calories but also radically alter the proportions provided by protein, fat, and carbohydrate. In this country a healthy sedentary person may be supposed to consume some 2200 calories daily, made up of about 70 g. of protein, 60 g. of fat, and 350 g. of carbohydrate : protein supplies 12% of the calories, fat 24%, and carbohydrate 64%. On most reducing diets, however, the carbohydrate and fat will be restricted while the protein remains about the same ; and in a diet yielding 1000 calories protein may provide 30%, fat 37%, and carbohydrate 33%. Finally, Lyon and Dunlop (1932) observed that patients on isocaloric reducing diets lost weight more rapidly when the largest proportion of the calories was supplied by fat than when it was supplied by carbohydrate. Anderson (1944) attributed these findings to the different amounts of salt (causing water retention) in the diets used by these workers. More recently, Pennington (1951, 1954) has recommended high-fat diets in the treatment of obesity. It therefore seemed important to establish which factor has the greater effectrestriction of calories, or alteration in the proportions of protein, fat, and carbohydrate in the diet.


Discussion 


If these observations are correct, there seems to be only one reasonable explanation-namely, that the composition of the diet can alter the expenditure of calories in obese persons, increasing it when fat and protein are given, and decreasing it when carbohydrate is given. This is not surprising as regards protein, whose specific dynamic action has long been recognised. It is, however, surprising as regards fat, whose action in this respect seems to be even greater than that of protein. Direct confirmation of such altered metabolism is hard to obtain. The B.M.R., for example, is measured at a time of day and under .other conditions specifically designed to eliminate the effect of diet or reduce it to a minimum. In some patients the B.M.B. was measured at the beginning and at the end of each dietary period. Table vin shows that neither variation in calories nor variation of the composition of the diet with a constant intake of calories significantly changed the B.M.R. during these short dietary periods.


Summary 

1. Loss of weight can be successfully achieved in obese patients by numerous diets, most of which restrict calorie intake. At the same time almost all such diets alter the proportion of protein, carbohydrate, and fat as compared with the normal, restricting carbohydrate and fat in particular. It seemed desirable to investigate which factor was of the greatest importance in weight reduction-calorie restriction or alteration in the composition of the diet. 

2. The rate of weight-loss has been shown to be proportional to the deficiency in calorie intake when the proportions of fat, carbohydrate, and protein in the diet are kept constant at each level of calorie restriction. 

3. When calorie intake was constant at 1000 per day, however, the rate of weight-loss varied greatly on diets of different composition. It was most rapid with high-fat diets ; it was less rapid with high-protein diets ; and weight could be maintained for short periods on diets of 1000-calorie value given chiefly in the form of carbohydrate. 

4. At a level of intake of 2000 calories per day, weight was maintained or increased in four out of five obese patients. In these same subjects significant weight-loss occurred when calorie intake was raised to 2600 per day, provided this intake was given mainly in the form of fat and protein. 

5. No defect in absorption of these experimental diets occurred to account for the weight-loss. There was neither loss of body-protein stores nor of carbohydrate stores to a degree which significantly contributed to the reduction in weight. 

6. The weight lost on these diets appeared to be partly derived from the total body-water (30-50%) and the remainder from body-fat (50-70%). 

7. As the rate of weight-loss varied so markedly with the composition of the diets on a constant calorie intake, it is suggested that obese patients must alter their metabolism in response to the contents of the diet. The rate of insensible loss of water has been shown to rise with high-fat and high-protein diets and to fall with highcarbohydrate diets. This supports the suggestion that an alteration in metabolism takes place.

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