06 December 2008

When leptin levels in the blood increase, the brain will give signals to us to stop eating. Leptin affects our weight and our appetites as well as being affected by total body fat levels, leptin levels will rise and fall quite rapidly in response to both overfeeding and underfeeding. But since obesity isn’t the result of a lack of leptin, it is a lack of response to leptin, and obese individuals tend to have more and larger leptin-producing fat cells than thinner people, their leptin levels increase substantially with every pound of additional weight gain. This is illustrated below.

Leptin Research with Mice
Mice lacking leptin ate voraciously and grew enormously fat; leptin injections made them stop eating and slim down. The discovery led researchers to think that fat people might also lack leptin, and that it could make them lose weight. But it was not so. Scientists found that most fat people had lots of leptin, and giving them more had little effect.

Researchers at the Oregon National Primate Research Center conducted a study in mice involving two separate groups that were fed high-fat and low-fat diets. The high-fat diet group developed symptoms of diabetes and obesity while the low-fat diet group did not. The researchers tested cells which conduct nerve impulses and found the cells behaved as if there was no leptin present, even though levels were 40-times higher than in normal mice.

This is due to obese people becoming resistant to leptin’s signal. When the brain fails to sense the leptin hormone’s signal correctly it thinks that more fat is required, even though we have enough, and fat begins to accumulate while metabolism slows down. Some scientists think that either leptin is not transported through the blood-brain barrier properly or the brain is not interpreting the signals properly.

With the regular discovery of hormones involved in regulating body weight it is a diverse and rapidly expanding field.

Obesity Clinics Test Leptin Injections
A randomized, controlled trial performed in six different obesity clinics looked at the effects of leptin on 73 obese men and women. Researchers reported in The Journal of the American Medical Association that daily injections of leptin led to a mean weight loss of 15 pounds in a 24-week treatment period. More than 95 percent of the lost weight was from body fat. There was considerable variation in the amount of weight that individual subjects lost during the treatment. Subjects who took the highest daily doses of leptin also lost the most weight.

It is important to note that during this study, the research subjects also followed a weight reduction diet; however, those subjects in the placebo group who did not receive leptin only lost an average of 3.75 pounds in 24 weeks. The researchers believe that the effect of the diet was minimal since subjects who took leptin lost almost five times as much weight.

See Does More Leptin Help to Accelerate Weight Loss? for more information.
See Leptin for Weight Loss for more information.
See Is it Effective Taking Leptin as Weight Loss Pill? for more information.

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