Leptin is a hormone that is naturally produced by the fat cells in the body, also known as adipocytes. Leptin plays a major role in suppressing the appetite and regulating metabolism. When released into the bloodstream it acts on receptors in the brain, signalling that the body has had enough to eat. A feeling of fullness is experienced, which helps regulate our eating behaviour and helps control our energy balance. It is widely known that leptin helps the body utilise fat stores. Your leptin levels need to be high in order to burn fat, and when leptin levels decrease, your fat stores increase.
When people lose weight through food restriction alone, there is a subsequent reduction in metabolic rate because there is a loss of both fat and lean body tissue. Leptin levels decline and the metabolism slows down in response to receiving less food energy. However, leptin may play a role in sparing lean muscle mass when dieting, by causing weight to only be lost from fat deposits. Additionally, leptin does not decrease the metabolism, even when caloric intake is reduced.
Leptin and Obesity
Many obese people make attempts at weight loss but eventually gain the weight back. This is likely to be due to the fact that leptin production is reduced when weight is lost through dieting alone. Low leptin levels trigger fat storage rather than fat burning, as low food intake triggers the starvation mode. Leptin supplementation, when taken alongside a caloric-restricted diet, does not produce a decline in metabolism and is a more successful method in maintaining weight loss in the long-term.
A leptin insensitivity is commonly considered the underlying cause of obesity in humans, predisposing affected individuals to easily gain weight. To naturally boost leptin levels, eat small meals that are evenly spread out throughout the day and consume adequate amounts of whole grains, fruits, vegetables and other nutritionally valuable foods. Maintaining proper metabolic function is the key to keeping hormones in balance and producing ideal levels of leptin for appetite regulation and weight management.
When Leptin was first discovered it was considered the anti-obesity hormone. Through decreased food intake and increased energy expenditure, which results in rapid weight loss, lean muscle mass can be preserved.
Most people have noticed that a diet usually starts out quite easy, particularly if one is obese. However, as the duration of the diet is extended, cravings start to set in and they become more and more intense. We recommend that “cheat” days be employed to prevent this, as they reset hormonal levels and glycogen levels, but also for your mental wellbeing.
Decreases in leptin are strongly associated with increased sensations of hunger. The lower your leptin levels go, the more severe the sensations of hunger are.
Like hunger control, fat loss is remarkably easier at the beginning of a diet. However, it invariably slows, and if appropriate steps are not taken, it stops. Low leptin levels are correlated with decreases in resting energy expenditure.
In dieters, it is a common practice that when they reach a plateau (leptin levels are low) they cut their calorie intake even further, while increasing their physical activity. Unfortunately, this is just going to decrease leptin levels even more, making things that much worse.
What you should be doing is the exact opposite. We do this by employing a cheat meal into our clients’ plans. The cheat meal is a planned ‘non calorie restricted’ refeed. These refeeds should be done before signs of low leptin levels become apparent. We recommend this be every 7 days, and it is usually followed by an intermittent fasting period.
The primary purpose of the refeed is to boost depleted glycogen levels and therefore your metabolism. There are arguments that any refeed should only be 50% higher in calorie intake than the diet you are on. We believe that restrictions on refeeds are not necessary, unless your leptin levels are drastically low, in which case you would refeed more regularly. With a high calorie refeed, usually in the form of quality carbohydrates, proteins and good fats, you can keep your metabolism firing and leptin levels at a more sustainable level.
Assuming we have not created drastically low leptin levels, our refeed will be 20-50% ABOVE maintenance, for 12-48 hours. The higher the calories, the shorter the refeed, and there are arguments in support of this. If they are drastically low, 5-7 days of 20% above maintenance, is recommended. In general, the lower you are below your natural body fat set point, and the longer or more drastic your diet, the more frequent the refeed.
Our primary macronutrient will be carbohydrate, which enters the blood as glucose. Insulin also potentiates glucose stimulated leptin production, therefore high GI carbs are most ideal. Protein should be 1g/lb, and a bit of fat and fructose from foods that you enjoy is acceptable, but the rest is non-fructose carbohydrates.
The Fed State
Leptin is responsible for the anabolic hormonal setting that is associated with the so-called “fed state”, and the lack thereof during underfeeding. Therefore, in addition to its high importance in our fat loss efforts, it is extremely important in increasing and maintaining muscle mass.
The reason we lose muscle mass when dieting, despite resistance training and adequate protein intake, is hormonal. Hormones are also the reason we cannot gain our maximum amount of muscle without over eating, which in turn leads to some fat gains. With the exception of insulin, leptin controls these anabolic hormones and both insulin and leptin are mediated by glucose, therefore they go hand in hand.
Increased leptin levels lead to preferential refilling of liver glycogen stores, which is a prime indicator of the fed state, as well as an increase in testosterone and human growth hormone. It also blunts ACTH, which signals cortisol secretion in the adrenals and inhibits cortisol synthesis directly.
Though leptin is the master hormone, there are numerous other signals involved in adipostatic control — and this is where it REALLY gets complicated. Some of these signals are directly modulated by leptin (anorexic peptides are increased and orexigenic are decreased), while some are not. Some are redundant (meaning if they are taken out of the equation, something else takes over), while others are not. At last count, there were about 15 of them — cortisol, ghrelin, neuropeptide-Y, orexigen a & b, melanin-concentrating hormone (MCH), cotropin-releasing hormone (CRH), and agouti-related peptide (AgRP) are a few that come to mind — and there are almost certainly many more that we are not yet aware of.