Thermogenesis is the generation of heat from food energy. One particular type of thermogenesis is diet induced thermogenesis (DIT). Diet induced thermogenesis, sometimes referred to as the thermic effect of food (TEF), is the generation of heat directly as a result of food intake. Such increases in thermogenesis can be measured directly as heat rises following consumption of food. Evidence suggests that certain foods are able to stimulate thermogenesis to a greater degree than other foods. Protein for example, requires a larger amount of energy for its digestion, absorption and digestion compared with carbohydrate and this increases the thermogenic effect of protein. It has been reported that more palatable food is able to stimulate thermogenesis to a greater degree than an equal amount of bland food. Cafeteria snack type food for example has been shown to induce heightened thermogenic responses compared to a more normal higher quality diet. The effects of such palatable food has been investigated using rats.
For example, in one study1, rats were fed either an ad libitum highly palatable diet, normal rat chow or a highly palatable diet restricted to the same energy content as the normal rat chow diet. The researchers then analysed the response of the rats by measuring the thermogenic responses. The results confirmed previous findings in that the palatable food increased the thermogenic response of the rats compared to the normal rat chow, and significantly decreased the efficiency of the food in terms of supplying energy for work. The thermogenic responses in the rats were coupled to increases in the activity of brown adipose tissue (BAT), a type of adipose tissue associated with heat production. Noradrenaline levels also increased, suggesting that the androgenic hormonal system was possibly the cause of the increased thermogenic effect. Interestingly the degree of thermogenesis was not dependent on the amount of food ingested, as the ad libitum and restricted energy palatable diet stimulated thermogenesis to the same degree.
Dr Robert Barrington’s Comments: These results suggest that the palatability of the diet plays a considerable role in the thermogenic response to that food. This may suggest that there is a considerable psychological or cephalic component to energy utilisation in animals. That similar effects have been observed in other animals and humans suggest that the effect is consistent between mammals and may play a role in human nutrition. The sensory aspects of nutrition are often forgotten, but it has been known since the work of Pavlov that the mental aspects of nutrition have a significant influence on the physical. The cephalic phase of nutrition, the sight, thought, smell or texture of food can stimulate digestive and absorptive processes, and this stimulation can increase as the desirability of the food increases. Therefore it would be logical to expect that highly palatable food may stimulate enhanced physiological responses in rats, as was shown in this study with regard the thermic effects of food.
RdB
