Leptin and Weight Loss
Leptin, derived from the Greek word “leptos”, meaning thin, is a small hormone secreted by fat cells circulates in the blood, plays a role in the regulation of metabolism and appetite and is the major hormone secreted by fat tissue.
Leptin was discovered in the early nineties by studying mutant obese mice (Ob/Ob), which spontaneously arose in an American mouse laboratory in 1950. These mutant mice were obese, were over-eating and developed type II diabetes, all symptoms that resembled morbid obesity in humans.
Leptin binds to and interacts with six types of receptors, which are located in the appetite center of the brain (in the hypothalamus) and some peripheral tissues. Leptin cannot cross the blood-brain barrier and must be actively transported. How much of the hormone is transported into the central nervous system is dependent on its plasma concentration.
A small percentage of people have mutations in either the leptin gene, one its receptors or transport proteins, which results in obesity. Usually, leptin concentrations in these people are very high and it is thought that the bodies of these people are insensitive to the effects of leptin.
The appetite and metabolism control in these obese people may be disrupted, as their brain is not receiving the appropriate satiety signals. The result is increasingly larger fat stores and eventually the development of type II diabetes.
Recent studies found a link between lack of sleep and obesity: not enough sleep stimulates the production of a hormone called ghrelin, which in turn stimulates appetite by decreasing the levels of leptin.
It has been suggested that the natural hormone melatonin is able to increase leptin production in the presence of insulin. This is why a good night’s sleep is important for weight control.
While most people are advised to lower their intake of food products containing high-fructose corn syrup, a recent study found that a diet high in fructose could induce leptin resistance, a condition that can quickly result in obesity, especially when combined with a high-fat and high-calorie diet.
This condition occurs when the appetite center of the brain does not respond appropriately by reducing food intake. This is the reason why it is vital to eliminate as much food products containing high-fructose corn syrup from your diet as possible. Reducing calories by reducing the intake of fructose and eating a low-fat diet are important in the battle against weight gain.
Shapiro, A. et al. (2008) Fructose-induced leptin resistance exacerbates weight gain in response to subsequent high-fat feeding. Am J Physiol Regul Integr Comp Physiol.295: R1370-5.