Steve McDermott
New Member
I was looking at the Harvard Medical School newsletter (Focus) the other day and what is on the front page? "Leptin Serves Body as Energy Signal. Study confirms in humans that the hormone helps regulate reproduction. Much of the research on leptin has been done on obese people in the fed state. This study looked at leptin levels in starvation conditions. This is much more relevant to what bodybuilders do while dieting.
The study, which will be in the May 1st Journal of Clinical Investigation involved 8 healthy men. They spent four, five day sessions in the hospitals research center. They first were fed a maintenance level diet to determine baseline hormone levels. Then during the next three visits they spent 3 of the 5 days fasting. At the second visit they were injected with a plecebo and at the third they were injected with low doses of leptin. At the final visit they were injected with enough leptin to restore levels to baseline. During the experiment blood was drawn every 15 minutes (even while asleep) to monitor hormone fluctuations.
During the starvation periods testosterone levels droped significantly along with a drop in leptin (expected). When leptin was returned to normal levels via injection, testosterone levels returned fully to baseline. This clearly showed that leptin has a direct effect on the HPTA. The study also showed a relationship between leptin and the The thyroid hormones. Replacing leptin also had a mild effect on IGF1 levels. It had no effect on growth hormone or cortisol levels.
This was very interesting to me in that when dieting with refeeds, I have found that I can add small amounts of muscle (given that the refeeds are adequate enough to boost leptin signigicantly). I also have noticed that dieting without refeeds has not yielded similar results. It also makes sense that in times of starvation that the body switches its focus from reproduction to survival.
The study, which will be in the May 1st Journal of Clinical Investigation involved 8 healthy men. They spent four, five day sessions in the hospitals research center. They first were fed a maintenance level diet to determine baseline hormone levels. Then during the next three visits they spent 3 of the 5 days fasting. At the second visit they were injected with a plecebo and at the third they were injected with low doses of leptin. At the final visit they were injected with enough leptin to restore levels to baseline. During the experiment blood was drawn every 15 minutes (even while asleep) to monitor hormone fluctuations.
During the starvation periods testosterone levels droped significantly along with a drop in leptin (expected). When leptin was returned to normal levels via injection, testosterone levels returned fully to baseline. This clearly showed that leptin has a direct effect on the HPTA. The study also showed a relationship between leptin and the The thyroid hormones. Replacing leptin also had a mild effect on IGF1 levels. It had no effect on growth hormone or cortisol levels.
This was very interesting to me in that when dieting with refeeds, I have found that I can add small amounts of muscle (given that the refeeds are adequate enough to boost leptin signigicantly). I also have noticed that dieting without refeeds has not yielded similar results. It also makes sense that in times of starvation that the body switches its focus from reproduction to survival.