The key hormone for a healthy weight

What is Leptin?

Leptin is a hormone essential for regulating food intake and therefore for weight control. It belongs to the proteohormones, composed of more than 100 different amino acids. Often called the “satiation hormone”, leptin is produced mainly in fat cells (adipocytes) and released into the bloodstream. The number of fat cells in the body largely determines leptin levels: the more fat stores present, the higher the hormone level.

Besides fat cells, leptin is also produced in small amounts in the bone marrow, skeletal muscle, the gastric mucosa and skin cells. As soon as food reaches the stomach, it is released by the stomach wall about 15 minutes after the meal. This hormonal regulation plays an important role in metabolism.

How does Leptin work?

In a healthy person, leptin levels are regulated to keep the body's total energy reserves in balance. When fat cells are well filled, they secrete leptin and signal: “We are full!” As mentioned, leptin is produced in fat cells. The more fat cells there are, the more leptin is secreted — and vice versa.

Leptin travels via the bloodstream to its target cells in the hypothalamus to trigger specific effects. It can bind to target receptors in the hypothalamus and has two different binding sites that trigger two different processes — one group of nerve cells produces appetite-suppressing messengers, while the other group produces appetite-stimulating neuropeptides.

The fundamental aim of this signaling is the generation of a feeling of satiety. Leptin signals the brain that no further food is needed and thus prevents eating beyond the body's needs.

When leptin is active in the body, energy-consuming processes are set in motion. These include an increased metabolic rate, enhanced activity of the sympathetic nervous system and the thyroid, as well as regeneration and building of tissues such as muscle or skin.

Leptin resistance leads to elevated leptin levels in the bloodstream, which favour a persistent pro-inflammatory activation of the immune system. This can lead to chronic, “silent” inflammations that may develop into contemporary disease patterns.

How can you naturally raise leptin levels?

Leptin levels are strongly influenced by how full the fat cells are, which depends on food intake. Leptin is directly linked to the presence of fat stores — the more fat cells, the more leptin can be produced. In this way leptin levels provide information about available energy reserves and indicate how the body is being supplied with energy.

Unfortunately, there are no natural foods that contain leptin, since this hormone is produced and released exclusively by the body's own fat cells.

The idea of hormone supplementation, taking additional leptin to boost fat burning and suppress hunger, may seem appealing. However, such additional leptin intake and the resulting rise in leptin levels would very likely lead to leptin resistance.

Much more important is the sensitisation of the target cells in the hypothalamus to leptin's signal. The satiation effect primarily depends on how well the different target receptors in the hypothalamus are able to recognise the messenger's signal.

Therefore, it is recommended not to take additional leptin supplements. The most effective measures to keep leptin levels stable and to improve receptor function in the long term are nutrition, exercise and sleep.

How is leptin measured?

Leptin can be easily measured by a blood sample. Even simpler is the measurement of waist circumference at the navel. Ideally this should not exceed half of body height. For a height of 180 cm the waist circumference should therefore be a maximum of 90 cm. For well-trained competitive athletes a reduction of 15% may be the target. If the waist circumference is larger than 50% of body height, it can be assumed that fat has already been deposited in the organs.

What are the symptoms of leptin resistance?

With overweight it is common that high leptin levels do not lead to satiety or weight loss. As abdominal fat increases, the body produces more leptin. Over time the brain develops resistance to the hormone, largely due to constantly elevated leptin levels in the bloodstream: people with severe overweight feel hungry despite high leptin levels and do not automatically lose weight. Although leptin binds at the expected sites on nerve cells, the information is not converted into a satiety signal. There is a blockage at an as yet unclear point that prevents the signal from passing through.

Signs of leptin resistance can include: increased abdominal fat, high blood pressure, eating disorders, frequent cold feet or hands, fatigue, a high meal frequency (more than 21 meals per week), absence of fever during infections, menstrual problems as well as persistent and frequent feelings of hunger.

How to keep your leptin level stable: practical tips

• Various studies suggest that a balanced diet and regular physical activity can help restore leptin sensitivity in the brain. Weight loss and reduction of body fat are the decisive steps to restore hormonal balance in cases of overweight and leptin resistance.
• Try the keto diet. The ketogenic diet, characterised by low carbohydrate intake and relatively higher fat, leads in most cases to significant weight loss in people with severe overweight. Additionally, compared with other diets, it is reported to provide increased feelings of satiety. This is due to improved leptin sensitivity and the direct influence of ketones on the brain and possible links with the gut microbiota.
• Certain foods may promote leptin release and thus contribute to longer-lasting satiety and less cravings during weight loss. Examples of foods that can stimulate leptin release include: whole grain products such as wholemeal bread, whole grain pasta or rice; fibre- and antioxidant-rich vegetables such as spinach, broccoli or legumes; citrus fruits; sea fish such as salmon or tuna.
• Recommended foods in leptin resistance also include: avocado, chili, eggs, garlic, apricots, sea fish, seafood and shellfish, mushrooms, quinces, red pepper, saffron, snails, tropical fruits (especially mango, papaya, melon), tamarind, root vegetables and onions.
• Strictly avoid: fructose, table sugar, high-calorie foods (225-275 kcal/100g), industrially processed convenience foods and fruit juices, high meal frequency, intensively farmed meat, vegetable oils such as corn germ, safflower, sunflower and peanut oil, as well as sugary drinks and energy drinks.
• Slowing down eating pace and chewing thoroughly may sound trivial but are crucial. Eat slowly, chew each bite consciously and do not swallow hastily. You need to relearn to consciously perceive the feeling of satiety.
• If you find it hard to restrain yourself, use a timer: allow 20 minutes for each meal. That is roughly the time your body needs to develop a feeling of fullness. It may seem long at first, but if you eat mindfully and chew well, your eating pace will adjust over time.
• Choose the right portion size. Estimating the correct portion is not easy. You can weigh food or use your hands as a measuring aid. The size of your hand gives you an idea of how much fruit, chips or oats you should eat.
• High-protein foods, such as eggs, poultry, tofu or low-fat quark, are excellent satiating options because they keep you full significantly longer than carbohydrate- or fat-rich foods. The body takes more time to digest protein and to break down its building blocks, the amino acids. This helps prevent, among other things, cravings.
• High-fibre foods provide long-lasting satiety, support weight loss according to studies and aid digestion. Insoluble fibres like oats, legumes or whole grain products increase food volume due to their swelling capacity, stretching stomach and intestines. Gastric emptying is delayed, leading to faster and longer-lasting satiety.
• Avoid crash diets. Instead of starving yourself, aim for a consistent, moderate energy deficit. If you suddenly eat much less, ghrelin concentration rises while leptin concentration falls. This triggers cravings.
• Regular physical activity can increase leptin sensitivity. You not only burn calories but also feel more satisfied. In addition, effective high-intensity interval training (HIIT) temporarily lowers blood concentrations of the hunger hormone ghrelin, resulting in reduced hunger.
• At rest, the body somewhat recharges leptin. Eight hours of sleep per night increase the chance to regulate the satiation hormone level.
• If you are considering appetite suppressants, fat blockers or satiety capsules to control persistent hunger, note the following. Fat binders or blockers such as chitosan can inhibit fat digestion but also negatively affect the absorption of fat-soluble vitamins and essential fatty acids. Preparations with expanding fibres like pectin or glucomannan can help increase stomach volume and thus create a feeling of fullness.

In a world constantly seeking ways to promote healthy eating habits and combat overweight, leptin undoubtedly plays a central role. With advancing research, new ways may be found to support the balance of our hormonal system. Even small steps, however, can already have a large effect today and positively influence leptin health.