The December 2010 Nutrition Action Healthletter provides some new and enlightening scientific evidence that establishing a healthy weight is even more complicated than previously thought. Forget what so-called experts say about calorie consumption and energy expenditure being the sole or major determinant of weight. Here’s the real deal.

These research conclusions are from Eric Ravussin, head of the Division of Health and Performance Enhancement at the Pennington Biomedical Research Center in Baton Rouge, Louisiana:
“When people lose weight, their leptin (the hormone produced by fat cells which lets the brain know when your body has stocked up enough fat) goes way down, and the body interprets that as a state of starvation. When the survival of an organism is at stake, the body has redundant systems to avoid starving.”
“When people lose 10-20% of their body weight, their metabolic rate drops and becomes thrifty. So they need fewer calories to stay at their lower weight than people who have always weighed that much. That puts the dieters at higher risk of regaining the lost weight. And they’re hungry most of the time. So it’s a constant struggle.”
The bodies of some obese people “produce leptin in abundance but the leptin doesn’t work. In fact, many people are resistant to both leptin and insulin.”
“Genes affect both energy intake and energy expenditure. The metabolic rate of people of the same sex, age and body size may vary by as much as 500 calories per day.”
“Scientists are looking at about 10 different viruses that may contribute to obesity.”

What does this research mean for you? What you’ve known for years—that the eating and weight game is not played on an even playing field. When you’ve noticed that a friend seems to eat twice as much as you and not gain weight, your perceptions may be accurate. When your weight reaches a plateau and no matter how much you cut back, you can’t lose a pound, your body chemistry is reacting as if you’re in starvation mode. When you exercise more than many folks around you and still can’t shed significant pounds, it could be that your metabolism is different than theirs.

The upshot is to stop comparing yourself to other people, focus on what works for you, do what you realistically can, don’t give up, and be grateful for your successes.