In our clinic we spend a lot of time thinking and talking to our patients about the hormone leptin.
In another instance of the concordance of important findings to obesity science and eating disorder science, the study of leptin and body weight, leptin and menstrual function and now leptin and mood, has revealed relevance to both of these groups. According to an article titled Leptin Predicts Decreased Depressive Symptoms, from the Neuroendocrine Unit of the Department of Psychiatry of Mass General, Lawson E, Miller K et al., leptin levels also affect depression and anxiety levels.
Leptin was discovered by animal lab researchers working in the field of obesity. Leptin is a hormone secreted by fat cells which has receptor sites throughout the body and brain, in areas relevant to the regulation of appetite and, interestingly, also in brain areas thought to regulate the emotions (e.g. limbic system). It appears to have been one of several critical hormones evolutionarily important in protecting us during times of famine.
For most of mankind’s history famines have been more common than times of plenty, and the brain is built to try and withstand this assault on our survival. As our body fat stores diminish, so does leptin. This signals the brain to turn on other hormones responsible for increasing our appetite and food foraging behaviors. We are forced to seek food by the brain. Leptin also has a dampening effect on some of the hormones of reproduction, such as LH (luteinizing hormone), and through them suppresses menstruation. In other words, the brain judges times of famine to be poor times to reproduce.
As part of Kartini Clinic’s Weight Restoration 2.0, we routinely measure leptin levels of our patients. At the start of re-feeding these levels will be very suppressed. As body weight goes up, leptin levels begin to rise and other hormones normalize, eventually resulting in a balancing of those hormones which drive us to eat and those which tell us we have eaten enough. At least that’s how it’s supposed to work. In some patients, for reasons too complex to go into here, leptin remains suppressed. It can be suppressed by aerobic exercise and by dieting (restricting), even for short periods of time. For these patients with prolonged suppression of leptin menstruation does not return.
But that’s only part of the story. Back to the article. There investigators looked at the relationship between anxiety, depression and leptin levels and they found that low leptin levels correlated with depression and anxiety, independent of body weight, in four groups: those with anorexia nervosa, those with lack of menstruation for other reasons,(“hypothalamic amenorrhea”), those who were overweight/obese and a control group with none of these conditions.
The fact that mood is adversely affected by low leptin levels is important to full restoration of health in our patients. Many of our patients with AN are focused on normalization of their leptin levels as their ticket to being allowed to return to exercise. But it may turn out to be more important that normalizing leptin levels (through adequate fueling and rest) has a potential to improve mood and sense of well-being. After all, it’s about happiness, right?