Broda Barnes on the thyroid and obesity (extract from his book):

“For many years, the standard diet prescribed by many physicians has been one with high protein content and little fat. The basis for it has been the fact that there are more calories per unit of weight in fat than in other foodstuffs.

What was not realized was the effect of a diet high in protein on thyroid function which explain why many patients have failed to lose weight on as few as 800 calories a day of such a diet and have been accused of cheating on their diet when, in fact, they did no cheating.

In the experiments conducted on myself, I found that when the intake of carbohydrate and fat was kept low and I ate mostly veal and turkey, diarrhoea soon developed and I had feelings of malaise and illness. On the other hand, when the diet was changed so that it was low in fat but high in protein and with enough carbohydrates to prevent diarrhoea, symptoms of hypothyroidism appeared. Cholesterol levels in the blood became elevated and in order to keep it within normal range, four additional grains of thyroid daily were needed. Apparently, a diet high in protein requires additional thyroid for its metabolism. There were no symptoms of hyperthyroidism in spite of the extra thyroid until the diet was cut back to a normal amount of protein. Then typical hyperthyroidism appeared and the extra thyroid had to be discontinued.

It seems clear that a diet quite high in protein utilizes available thyroid hormone. Two studies in the medical literature indicate the excess protein lowers the basal metabolism. This may explain why so few people have been successful in losing weight on the standard types of diets. With extra thyroid needed for utilization of protein, the metabolism could fall to the point that 800 calories a day would maintain existing weight rather than lead to weight loss.

This would also explain why some physicians specializing in weight reduction and using high-protein diets in their programs also use huge doses of thyroid without any apparent harm to their patients.”