Chronic stresses cause weight gain. The culprit? A hormone called Neuropeptide Y. Stress turns on a switch to this chemical messenger found in body fat. It increases appetite, especially for carbohydrate-rich foods, and causes the body to convert extra calories into dangerous belly fat.

The amount of weight gain increased three-fold when a high fat, high sugar diet was given to lab mice subjected to chronic stress. It also caused metabolic syndrome (glucose intolerance, high cholesterol, high blood pressure and inflammation).

However, when researchers blocked the effects of neuropeptide Y on the animals, it reduced stress-induced visceral fat by 50 percent, at the same amount of activity and food!

In humans, studies have shown that there is a direct relationship between work stress and risk of obesity. More specifically, stress increased abdominal fat.

Anxiety and depression also increase the risk of obesity. Insulin and blood-sugar levels tend to be higher in those who are anxious and depressed.

Neuropeptide Y stimulates growth of new blood vessels (angiogenesis), which leads to weight gain and increased cancer risk. The action of this hormone may help to explain the relationship between obesity and increased cancer risk.

Several studies have shown that a diet low in fat and high in fruits, vegetables, whole grains, legumes, omega?3 fatty acids and soy products inhibits angiogenesis.

Stress affects how we eat, which in turns affects how we feel. In fact, a recent study published in the Journal of Marketing found that people who are feeling unhappy eat larger amounts of foods they consider tasty and unhealthy, compared to happy people.

Stress is a chemical event that makes us fat and sick. When we are fat and sick, we get more stressed. Which makes us fatter, and sicker. How do we get out of this loop then? Perhaps the first step is learning how to handle stress skillfully. That consists of acknowledging the situation, managing our environment, training ourselves (e.g., mindfulness based stress reduction, heart rate variability methods), and perhaps most importantly as a first step, making a commitment to learning how to change for the better.

Easier said than done. I think it really has to be a coordination of many different variables within our control.

While medical approaches emphasize hunger and satiety as the root of obesity, they are usually not the most significant causes of overeating. “Socially informed perceptions of which foods are appropriate to eat, when they should be eaten and how much should be consumed have a greater impact on our food intake than feelings of hunger or fullness,” according to a University of Toronto study published in Physiology & Behavior.

Environmental cues shape eating decisions, in addition to physical or nutritional needs. The choices that our fellow eaters make often determine how much we eat. Norms may become elevated depending on the social context. For example, an individual may refuse second helpings at a formal meal but accept them when eating at an all-you-can-eat buffet or among family and close friends.

“People are often rudderless in eating situations and they look to the activity of others, their own previous behavior or other social cues to guide them and thereby consume more than they need. Frequently, eating occurs within what we have termed a zone of biological indifference, in which the individual is neither genuinely hungry nor genuinely sated. Without any particular biological reason to start, continue or stop eating, we are particularly vulnerable to socially based influences.”

“Norms of appropriateness have yet to achieve mainstream status in current medical research into obesity and overeating and in public policy concerned with curbing the obesity epidemic. No one seems to be aware of the power that social influence has on eating, but if such considerations are integrated more deeply into this area, we may see some more practical results.”

I think that the concept of the “zone of biological indifference” is important in weight management, because it underlines the power of the social context surrounding eating. Most people eat not because they are hungry, but because other people just happen to be eating as well. It all goes back to developing awareness, and the skill of making consistent conscious choices about food. Not an easy task, obviously.