Professor of Pediatrics at the Harvard Medical School and a Professor of Nutrition at the Harvard School of Public Health

Does overeating cause us to get fat? Or could it be that getting fat causes us to overeat?

It used to be held as basic common sense in weight loss that cutting calories is the path to weight loss. Or more precisely, consuming fewer calories than you are burning.

In an article in NY Times, David Ludwig a professor of pediatrics at Harvard Medical School, and Mark Friedman vice president of research at the Nutrition Science Initiative(US), challenge this idea saying we may be confusing cause and effect.

While calorie counting may be a simple truth, it does not help people to achieve long term weight loss because there are feedback mechanisms that kick in and work against you.

The researchers say that for both over- and under-eating, these responses tend to push weight back to where it started — prompting some obesity researchers to think in terms of a body weight “set point” that seems to be predetermined by our genes.

If this were true then a persons weight would return to its starting point whatever the diet, so they ask ‘why have obesity rates — which, for adults, are almost three times what they were in the 1960s — increased so much?’

As it turns out, many biological factors affect the storage of calories in fat cells, including genetics, levels of physical activity, sleep and stress. But one has an indisputably dominant role: the hormone insulin.

Insulin is a hormone that is released when you eat carbs. Its role is to regulate blood glucose levels by causing your muscles to take it up and use it for energy. But it also regulates how the body stores fat. So the higher the levels insulin are in your body, the more fat is stored rather than used for energy.

The increased amount of refined carbohydrates in our diets has led to insulin levels being elevated putting fats cells into storage overdrive and elicited obesity-promoting biological responses in a large number of people.

According to this view it is these environmental factors that have led our fat cells to ‘take in and store excessive amounts of glucose and other calorie rich compounds. Since fewer calories are available to fuel metabolism, the brain tells the body to increase calorie intake and save energy ‘.

Read the full article.