By controlling for individual and environmental influences on weight, such as income and health, they then measure whether food-price changes affect body-mass index (BMI).

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The study also took into account body mass index (BMI) - a measure which relates weight to height.

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The findings come from a study of nearly 1, 000 US people that looked at diet, calorie intake and body mass index (BMI) - a measure of obesity.

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It found every 10% rise in body mass index (BMI) - used as an indicator of body fat - led to a 4% drop of available vitamin D in the body.

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Unfortunately, the recent Journal of the American Medical Association publication analyzing life expectancy correlations to one imperfect calculation of relative weight (BMI, the body mass index) distracts readers all-too-eager to cling to its implications that being chubby is actually better.

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"The investigators examined changes in sugar-sweetened beverage consumption and then its association with change in body fatness or BMI (body mass index), and subsequent deaths from cardiovascular disease, diabetes and cancer, " says Rachel Johnson, professor of nutrition at the University of Vermont in Burlington and chair of the American Heart Assocation's Nutrition Committee, who was not involved in the study.

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Jain also gets his patients to use a body weight tracker called BMI by NutriSystem to track their body mass index, since depression is a mind-body disorder.

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