First of all, what is leptin?
Haven’t many of us fantasized about a magic pill we could take to solve our problems with excess weight? No such pill yet exists, but in the world of science and medicine, a hormone known as leptin shows much promise in unlocking the mysteries of obesity. Leptin is secreted by the body into the central nervous system, and it is known to influence both feeding behavior and energy expenditure. Translation: leptin can make you eat less or more, depending upon its level in your system, and it can control how much energy you burn.
Since we know that the amount you eat and the amount of energy you burn in physical activity are the two most significant factors in weight reduction, understanding how leptin works may soon play a major role in weight management.
Dr. Peter J. Havel from the University of California, Davis, undertook a major study that was published in 2000 by Proceedings of The Nutrition Society. This study gives us major insight into how leptin factors into weight control, overall.
So how does it work?
Leptin appears to act directly on the central nervous system to regulate food intake. It has also been described as a negative feedback signal to regulate an individual’s energy balance; that is, the amount of energy a person takes in through calories versus how much energy he or she burns through physical activity. Studies with mice have found that administering doses of leptin resulted in increased body temperatures and greater physical activity. Other studies have found that leptin may also have an effect upon metabolism.
Leptin is produced by your body’s adipose tissue. In layman’s terms, adipose tissue is body fat. The amount of leptin produced by your adipose tissue is directly controlled by your body’s insulin levels. The more insulin your body releases, the more leptin is produced.
By the same token, if your body is insulin-deficient (as is found in people with diabetes), leptin levels are also significantly decreased. Genetic and biological factors may also affect levels of leptin production – even your gender and percentage of body fat play a role. In order to lose weight, you need both a normal level of leptin production and the ability for it to effectively take action within your body. Bottom line: the more leptin you have circulating in your body, the more effectively you may be able to control your appetite and energy.
Your body’s natural weight regulation
Research studies have found that most people seem to have a built-in ability to regulate their weight. Even with occasional over- or under-eating, most individuals’ weight will tend to fluctuate by only a few pounds. If an individual is forced to overeat significantly or be deprived of exercise, short-term weight gain will occur. But after the individual returns to normal levels of eating or exercise, the body will tend to return to its original “set point” weight.
However, animal studies found that some animals did not appear to have this ability to self-regulate, and their ability to produce or process leptin and other related hormones was found to be much less than normal. Research is finding that the same may very well be true with humans. Ironically, significantly overweight people tend to have unusually high concentrations of circulating leptin in their bodies. They appear to be resistant to leptin’s effects, much like Type II diabetics are resistant to insulin.
Research in this area is examining how large concentrations of leptin due to greater body fat may result in a lack of sensitivity to leptin.
Using leptin to treat obesity
Researchers have found that energy (calories) consumed as fat may not directly stimulate insulin secretion, and therefore may not lead to leptin production. One scientific study found that decreases in leptin that occurred during moderate calorie restriction were associated with feelings of increased hunger, regardless of the level of changes in body fat or calorie reduction. Conclusion? Both a very high-fat diet or an extremely low-calorie diet may affect the ability of your body to effectively use leptin in appetite control and energy management.
Because of the many research findings about the beneficial effects of leptin upon weigh control, the medical community is taking notice, and scientists are undertaking more human research. In one controlled weight-loss study, individuals who had leptin injected beneath their skin were found to experience significant weight loss over a nine-month period. This treatment appeared most effect in individuals whose leptin production had first been lowered through dieting.
1) If leptin production is decreased during highly restrictive weight-loss diets, later weight gain may be more likely; and
2) leptin dosages may possibly help maintain weight loss following successful dieting, by decreasing hunger and increasing the amount of energy an individual might burn.
The leptin system is clearly on the forefront of research into obesity causes and prevention. It may not be the magic pill, but is clearly has more secrets to reveal in the scientific puzzle of weight loss management. In the meantime, research in the field again reminds us that high-fat or very low-calorie diets are not the answer.
Proceedings of the Nutrition Society (2000), 59, 359–371