Lessons About Leptin, Weight, and Your Eating Environment
Sharon Palmer, R.D.

Environmental Nutrition Newsletter

If you've ever struggled with your weight, you know how difficult the fight is. You cut back on calories and drop 10 pounds, only to see your weight creep back up to where it was before. You could swear that your body has some magical number in mind for your weight despite your best efforts to keep it off. Now scientists believe your suspicions might actually be accurate.

The knowledge base is accumulating on leptin, a hormone produced by fat cells that tells your brain when it's time to cut back on eating.

FEEDING YOUR BODY WEIGHT

When you eat more food than your body needs, you store it as fat in fat cells. At the same time, your leptin levels rise and are released into the blood, signaling your brain that your body has had enough to eat and lowering your hunger pangs. Conversely, when you lose weight by reducing fat stores, your leptin levels go down, sending the message to your brain that you're in starvation mode and it's time eat to replenish your fat stores.

This is all part of the complicated dance of weight balance that the human body has evolved over thousands of years in order to survive. In our evolutionary journey, we struggled to find enough food to survive, so our bodies responded by developing a system to store an optimal amount of fat to draw upon in lean times.

Modern food clashes with weight balance. Today, we live in an unprecedented environment of excess calories, explains Martin G. Myers, Jr., M.D., Ph.D., associate professor of internal medicine at the University of Michigan Medical School. Myers, who studies the effects of leptin on diabetes, notes that if you operate in an environment of palatable, readily accessible foods, it drives you to reward-driven eating. In our past, we ate simple, whole foods like animal proteins and plants that we hunted, gathered, and cultivated; there were no hedonistic foods like Twinkies and French fries that promote overeating.

LEARNING ABOUT LEPTIN

First discovered in 1994, leptin led to much excitement in the world of obesity research.

"We understood that if you increase leptin, it acts as an appetite suppressant and pushes you to lose weight," says Myers. Scientists also discovered that when you lose weight, providing extra leptin through injections might help you boost levels to avoid weight re-gain.

Myers points to particularly interesting leptin research that came out of Columbia University, led by Rudolph Leibel, M.D., and Michael Rosenbaum, M.D. The research explored the effects of leptin on obese patients who were admitted to the hospital and fed a reduced-calorie diet to maintain a 10 percent weight reduction.

After the weight loss, as expected, leptin levels dropped and patients experienced the hallmark symptoms of starvation--decreased thyroid levels, energy expenditure and tolerance to cold temperatures, and increased hunger. But when leptin was replaced to achieve pre-weight loss levels, these "starvation" symptoms disappeared.

The researchers concluded that the body's state after weight-loss might as well be considered a leptin-deficient state, and that increasing leptin after weight loss might be an effective strategy to keep weight off long term.

Unfortunately, the results of leptin therapy in obese individuals were less successful than researchers had hoped. The problem is that if you already have a high level of leptin--obese people usually have plenty of it--adding more doesn't seem to do any good, explains Myers.

For example, if you have someone very obese, at a BMI (body mass index) of 35 or more, adding extra leptin doesn't appear to help with weight loss.

"Leptin doesn't work the way we want it to all of the time. Leptin can't do the job all by itself with environmental factors that promote overeating." However, recent clinical trials of a combination therapy of leptin and another hormone called amylin yielded promising clinical results of increased satiety in overweight people at a BMI of 35 and below, reports Myers. The studies are awaiting publication.

THE BOTTOM LINE

Does that mean you should throw in the towel if you're overweight and blame it all on leptin levels? Not at all. But don't fall for the latest wave of leptin diet book and supplement scams that offer to help you "master your leptin" with plant extracts and diet regimens.

Instead, take Myers' advice: "Manipulate your environment to promote a lower body weight. If you went from a hedonistic diet of pies and cookies and ate nutrient-rich, low-calorie foods, you would lose body weight. There would be less hedonistic drive to eat things you don't really need to eat. If you don't buy these foods and keep them around, then they aren't in your environment."

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