5 Slowing of metabolism and thermogenesis (the efficiency of mitochondria to produce energy and heat), so less energy is released by cells. Stress also stimulates ghrelin production, thereby increasing the tendency to snack and overeat.
Leptin – the hunger hormone that reduces appetite, which acts like a fuel gauge This peptide hormone is produced by fat cells and decreases appetite by communicating how much fat is stored and available to burn to the brain. It also has a long-term regulatory role with energy balance management, inducing weight loss. Leptin influences thyroid hormonal activity to manage metabolism. It works on the same part of the brain as ghrelin, but has opposite effects. People who have higher fat levels produce more leptin, however they tend to have a leptin resistance. This results in an imbalanced effect of ghrelin and leptin, which may lead to more weight gain and obesity.
Thyroid hormones – these manage and modulate metabolism These are secreted by the thyroid gland in the neck and help manage metabolic processes and energy production. They are affected by lifestyle, including diet, nutrition, exercise (HIIT – high intensity interval training), stress and sleep. The thyroid responds to internal and external factors and is one of the hormones responsible for metabolic adaptation when someone goes on a prolonged diet and exercise programme.
Adrenaline – known as the metabolic accelerator This is secreted by the adrenal gland and influences other hormones such as human growth hormone (HGH), cortisol and testosterone. The release of cortisol enhances its effects, however, prolonged release of adrenaline cannot be sustained and repeated stress results in exhaustion of adrenaline production, which then leaves behind an unbalanced release of cortisol. Unopposed chronic cortisol release can lead to insulin resistance, metabolic syndrome, central body fat accumulation, muscle loss and bone matrix loss. There can also be immuno-suppression, which can increase risk of infection, poor healing and even reduced surveillance against the chromosomal changes that result in cancer. Blood pressure and risk of heart disease can also increase.
Cortisol – known as the stress hormone This is secreted by the adrenal cortex. It has a beneficial effect in the acute stress response in situations of fight, flight or freeze response in the presence of danger, when balanced with adrenaline. In the chronic situation it is not balanced with adrenaline and so has the detrimental effects discussed above.
Human Growth Hormone (HGH) – known as the ‘anabolic’ stimulator This helps build muscle and burn fat at the same time. It works closely with adrenaline and cortisol to maintain vitality and youthfulness. These hormones are stimulated by HIIT (high intensity interval training) and Burst training (see also page 35) for less than thirty minutes at a time, maintaining a protein-adequate, balanced diet and getting plenty of sleep. Being sedentary, having poor sleep and eating a poorly balanced diet high in processed foods, as well as drinking excessive amounts of alcohol will damage the HGH production system. The production of HGH by the pituitary gland diminishes after the adolescent growth spurt and is only stimulated on demand after the mid-thirties as continuous levels of HGH in later life will accelerate the ageing process, disease processes and stimulate cancer cells.
Testosterone – known as the sculpting hormone This is produced at higher levels in men than in women and gives them their muscular shape. It works in conjunction with oestrogen (higher levels in women than men) to maintain a healthy body. The male testosterone/oestrogen ratio results in a muscular ‘V’ shape, while the female testosterone/oestrogen ratio results in the hourglass shape. Testosterone stimulates receptors all over the body to influence a state of wellbeing, sex drive, lean body mass, bone density, muscular strength and energy levels. Enough exercise, sex and sleep help maintain healthy levels. A diet with sufficient good-quality protein will also help maintain healthy levels.
Oestrogen – known as the feminising hormone This has a stronger influence on women, but is still present in men, though at lower levels. It is required to maintain a healthy lean body mass. To maintain appropriate levels of oestrogen, a healthy diet inclusive of healthy plant-based foods is necessary. Sufficient sleep and stress management is also important.
Progesterone – known as the friend of oestrogen This works with oestrogen to give the female shape and works to reduce the negative effects of cortisol. Sufficient sleep and stress management will help maintain this hormone.
Incretins – Known as the food sensors There are two of these in the body and they detect the ratio of food entering the small intestine and the relative amounts of fat, sugar, proteins and vegetable material entering the ilium:
1 GLP (glucagon-like peptide) is essentially a fat burner and sensitive to proteins and vegetables entering the small intestine.
2 GIP (glucose dependent insulinotropic – insulin-like – peptide) is a fat storer and sensitive to fat and sugars entering the small intestine.
Neuropeptide Y (NPY) – known as the fat amplifier This is produced and secreted by the nerves of the sympathetic nervous system and in the brain. It causes growth and amplification of fat tissue. In childhood, it determines the number of fat cells in the body in response to the calorific intake. After the pre-adolescent phase, it works like cortisol in increasing food intake and fat storage.
Irisin – known as the exercise-related fat burner This recently discovered hormone is secreted from muscle tissue after exercise. It increases fat burning and also improves cognitive function and feelings of general wellbeing. The most exciting effect of this hormone is that it appears to have an anti-ageing effect by lengthening telomeres, which can extend the life of cell lines, and so lengthen life expectancy and literally ‘turn back time’. Evidence shows that exercising big muscle groups and, to a lesser extent, aerobic exercise, increases the secretion of this hormone.
MOTS-c – known as the Mitochondrial-Derived Peptide This hormone works at the mitochondrial DNA level. It primarily targets muscle cells to modulate the mitochondrial DNA to promote metabolic homeostasis (balance). This in turn reduces obesity and insulin resistance. HIIT exercise on a regular basis (see also page 35) increases the number of mitochondria and so the effect of MOTS-c on the body.
HOW TO LOSE WEIGHT BY GETTING YOUR HUNGER HORMONES WORKING FOR YOU
1. Avoid calorie restriction diets. Prolonged calorie restriction increases ghrelin, reduces leptin and causes insulin and leptin resistance.
2. Avoid processed foods. These damage the metabolic system, causing insulin resistance, and also damage the leptin receptors.
3. Eat enough good-quality protein. This helps to control appetite and regulate ghrelin production. The recommended amount of protein is two portions per day. One portion is roughly the size and thickness of your palm for meat, fish and mycoprotein (such as Quorn), or two organic eggs.
4. Exercise is also important, but what type of exercise is the most effective? Historically, weight-loss advice was centred around low to moderate aerobic activity, such as walking, running, cycling or swimming. Research over the past ten years has actually shown that this type of exercise stimulates an increase in ghrelin and a reduction in leptin production, thereby stimulating hunger and increasing appetite. Prolonged aerobic exercise has also been shown to reduce testosterone levels. The initial increase in metabolism appears to stop after three months as a result of ‘metabolic adaptation’ and we hit a ‘wall’ with respect to weight loss; weight then starts to increase again, despite exercising. Prolonged aerobic exercise has also been shown to increase levels of cortisol. Research has shown that there are two types of exercise that (a) burn abdominal fat and control appetite and hunger, and (b) control weight gain in the short and long term. These are:
‘Burst training’. This involves exertion at 90 per cent of your maximum for thirty seconds for five sets, three times a week. Exercise intensely for thirty seconds then rest for forty seconds, before repeating the exercise. During the rest period,