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Leptin May Help Maintain Weight Loss

December 20, 2005

The hormone leptin may help dieters at a steady weight, although it has not proven successful in assisting with weight loss per se, according to new research. In a recent study, injecting leptins twice daily in people with a recent 10% body-weight loss appeared to reverse many metabolic processes that promote weight regain.

The study, conducted by Michael Rosenbaum, MD, and colleagues at Columbia University, was published in the December 1, 2005 issue of the Journal of Clinical Investigation and reported by MedPage Today on December 2, 2005.

The hormone leptin is produced by fat cells and involved in metabolism and hunger regulation. Discovered in 1994 in mice, leptin was originally believed to hold promise in helping obese people to lose weight.

Although studies of leptin as a weight-loss treatment were unsuccessful, further investigations have revealed that leptin is involved in regulating many metabolic processes in which body that is losing weight tries to maintain and restore fat reserves, according to Dr Rosenbaum and colleagues.

The metabolic processes that complicate maintaining weight-loss include skeletal muscle work efficiency, sympathetic nervous system activity and the actions of certain thyroid hormones, according to the researchers.

Clinical Trial

The study involved five men and five women whose average age was 32 years. Three participants were obese and the other seven weighed within the normal range. All participants had maintained their maximum lifetime weight for at least six months.

Study participants underwent an induced 10% weight loss resulting from a restricted-calorie liquid formula diet. Following weight loss, participants received a liquid formula diet designed to maintain their weight, while the researchers measured markers of leptin-regulated metabolism.

Finally, participants received twice-daily leptin injections for five weeks, and the researchers monitored their weight and metabolism.

Participants' 10% weight loss was associated with a reduction in leptin levels and activation of various metabolic processes that tend to promote regaining weight, including increased skeletal muscle work efficiency, decreased sympathetic nervous system activity and reduced circulating thyroid-hormone levels.

Significantly, when the original leptin levels were restored via injections, these metabolic processes were reversed.

Although ultimate weight change was not an outcome measure, participants' averaged weight decreased further while they received leptin injections.

"These responses suggest that the weight-reduced state may be regarded as a condition of relative leptin insufficiency. Prevention of weight regain might be achievable by strategies relevant to reversing this leptin-insufficient state," the investigators concluded, noting that "studies of longer duration are needed to determine whether chronic reactivation of the leptin axis following weight loss might assist in the long-term maintenance of a reduced body weight."

Low-dose leptin reverses skeletal muscle, autonomic, and neuroendocrine adaptations to maintenance of reduced weight. Rosenbaum M et al, Journal of Clinical Investigation, volume 115(12), pages 3579-3586, December 1, 2005.

Posted: December 2005