With nearly 65% of the adult population currently classified as overweight or obese and with calorically dense foods high in fat and carbohydrates readily available, investigating those factors that contribute to dieting failures is an important effort. In a study in the May 1st issue of Biological Psychiatry, researchers found that mice withdrawn from high-fat or high-carbohydrates diets became anxious and showed changes in their brains indicating higher stress levels.

Using a variety of standard measures of mouse behavior, researchers acclimated mice to either high-fat (HF) or high-carbohydrate (HC) diets, abruptly replaced those diets with standard chow, and observed behavioral changes. The brains of the mice were also examined for increases in corticotrophin releasing factor (CRF) levels which can indicate high stress levels.

Writing in the article, Tracy L. Bale, Ph.D., states, "Our behavioral, physiologic, biochemical, and molecular analyses support the hypothesis that preferred diets act as natural rewards and that withdrawal from such a diet can produce a heightened emotional state." Once deprived of their preferred diet, mice would overcome their natural aversion to bright environments to obtain the HF foods, even when standard food was available. The authors continue, "These results strongly support the hypothesis that an elevated emotional state produced after preferred-diet reduction provides sufficient drive to obtain a more preferred food in the face of aversive conditions, despite availability of alternative calories in the safer environment. Our results may suggest that, similar to the case of an individual who is in withdrawal from a rewarding substance, these mice effectively are displaying risk-taking behavior to obtain a highly desirable substance, supporting the powerful rewarding aspects of the HF food."

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Detailed information about cardiovascular and other health problems was sought from participants in the earlier trials. As part of this researchers found that participants who had cut back on salt during the trials tended to stick to a lower salt diet compared to those who had been in the control group. In total the researchers obtained information from 2415 (77.3%) participants, 200 of whom had reported some sort of cardiovascular problem.

The reduction in the risk of developing cardiovascular problems as a result of the sodium reduction intervention was substantial. The results showed these pre-hypertensive individuals were 25% less likely to develop cardiovascular problems over the course of the 10-15 years post-trial. There was also a 20% lower mortality rate. This risk reduction was evident in each trial.

To the authors knowledge this study is the first and only study of sufficient size and duration to assess the effects of a low salt diet on cardiovascular problems based on randomised trial data. It provides unique evidence that lowering salt in the diet might prevent cardiovascular disease.

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