In animal models high dairy intakes cause weight loss. The reason for this is not known. In addition, high dairy intakes in humans are associated with lower body weight suggesting that dairy contains some factor or factors that may be anti-obesogenic. However, the mixed results from some human studies suggests that environmental or genetic factors may modify the weight loss effects of dairy in some individuals. Stress is known to cause an increase in the release of cortisol. This occurs primarily through a flattening of the amplitude of the normal cortisol diurnal release pattern. In other words, the maximum cortisol release does not increase, but the minimum release rises to create a larger total release of cortisol. Energy restriction is a form of stress, and is is thought that diet induced stress may also flatten the amplitude of the normal cortisol release, causing fat accumulation and making future weight gain more likely. Dairy, perhaps because of its calcium content, may modify cortisol release and thus have an effect of cortisol induced weight changes.
Researchers have investigated the effects of high dairy diets on the release of cortisol in healthy human female subjects undertaking an energy restrictive diets1. Women were fed either an adequate amount of diary which was equivalent to 711 mL of milk per day or a low amount that was equivalent to 238 mL of milk per day over the course of a 12 week energy restrictive diet. The women then had their cortisol levels measured over the course of a day while they were given ad libitum access to food in a metabolic ward on a single occasion at the end of the 12 week period. The energy restrictive diet caused a reduction in the amplitude of the normal diurnal cortisol release over the course of the 12 week study. In addition the energy restriction also increased the cortisol release in response to a meal, but only in those subject consuming the low dairy diet. In the high dairy diet, the cortisol response to a meal was unchanged from baseline. These results suggest that dairy consumption is able to affect the function of the hypothalamo pituitary axis.
These results are interesting because they suggest that energy restriction is a form of stress that modifies the normal cortisol release pattern by raising the minimum amount of cortisol release, and this flattens the curve of the normal amplitude. Therefore energy restriction, as with all stress causes an increase in the cortisol release at times when it would normally be low. The reason for the ability of the high dairy diet to prevent the increase in meal induced cortisol release is not understood, but may explain the weight loss effects of dairy. The fact that the subjects on the high dairy diet lost both more body weight and more fat than those subjects on the low dairy diet suggests that this effect was not detrimental to the health. The weight loss effects of the high dairy diet in this study support other studies that show beneficial effects for dairy product consumption on body weight. Some of these weight loss effects might be due to the calcium in the milk, but other components such as conjugated linoleic acid may also contribute.
Dr Robert Barrington’s Nutritional Recommendation: High dairy diets have been shown to cause weight loss in animals and humans. This may relate to the calcium content of the dairy or may be due to other anti-obesity factors. Dairy is a healthy food and should be incorporated into a high quality diet if lactose intolerance is not present. Those with lactose intolerance can consume yoghurt and other fermented dairy products in small amounts where discomfort is not induced.
RdB
