A possible role for palatability of the food in diet-induced thermogenesis

A regulatory increase in energy expenditure, induced by excess intake of palatable food (cafeteria diet), is well documented. It has also been shown that excess feeding by gastric intubation, fails to enhance thermogenesis, suggesting that the palatability of the food could have a role in producing this regulatory response. A study was planned to find out if a palatable diet pair-fed with standard laboratory chow would produce diet-induced thermogenesis (DIT) and if the brown adipose tissue (BAT) was involved in this process.

Body weight gain, BAT activity and body temperature response to norepinephrine were measured in rats fed for 40 d either the standard laboratory pellets (control), a palatable high carbohydrate diet fed ad libitum and the same palatable diet but fed in restricted amounts to match the intake of the control group.

It was found that palatable food either fed ad libitum or pair-fed, increased DIT and reduced food efficiency (which is the body weight gain per 100 kj of food consumed). These responses were paralleled by increased BAT activity and enhanced response to noradrenaline. Since the DIT with pair-feeding was proportionally as large as with excess intake of the same food in the group fed ad libitum, it is concluded that the palatability of the food, rather than the excess intake per se, is responsible for the increased thermogenesis.

DIT was observed when palatable food was fed either ad libitum or in restricted amounts. It is suggested that the palatability of the diet rather than the quantity or composition of the ingested food is responsible for the DIT. It is also proposed that the excess energy expenditure due to sensory stimulation induced by palatable food, is directly related to an enhanced sympathetic activity which stimulates the BAT thermogenic capacity.