What is the role of hormones in obesity?

Obesity is an accumulation of an excessive amount of body fat, it is a complex disease. It is a medical problem that elevates the risk of different health problems and other diseases.

Obesity is often measured by Body Mass Index (BMI). According to World Health Organization BMI greater than or equal to 30 is known as obesity. Though BMI has some limitations.

Role of hormones in obesity:

Role of Ghrelin

This hormone influences eating behavior through direct or indirect effects on the brain. Neuropeptide-Y (NPY) is a hormone-like factor in the brain, that probably stimulates appetite. Although a number of signals can affect the ghrelin and leptin hormone, linked with NPY secretion to daily feeding pattern.

Ghrelin sometimes called a hunger hormone. It is polypeptide in nature and produced in the stomach. Ghrelin level increases before a meal and quickly falls after food intake. The increase in ghrelin level appears to stimulate NPY, thus encouraging feeding.

Role of Leptin

Leptin is regulated as a bodyweight regulatory hormone. It binds to a specific receptor in the brain and functions as lipostat. When the fat store in the adipose tissue is adequate leptin levels are high. This signals to restrict the feeding behavior and limit fat deposition. Leptin stimulates lipolysis and inhibits lipogenesis. Any genetic defect in leptin or its receptor will lead to obesity.

People who do not produce leptin due to genetic deficiency or who have defects in the leptin receptor show signs of poor appetite control, constant hunger, and eat more which leads to massive weight gain.

In obesity, there is sufficient leptin production but there is insensitivity or resistance of the adipose tissues to leptin. The concentration of leptin in the blood is usually proportional to the amount of stored fat. In the long-term regulation of energy balance leptin plays an important role. During starvation and weight loss leptin production from the adipose tissues decreased.

The decrease of leptin during prolong energy-restricted diet has been shown to be related to increase the sensation of hunger and therefore to the predisposition of weight regain after initially successful dieting. The effect of leptin deficiency can be improved by the administration of recombinant leptin.

Role of Thyroxin

Thyroxin is a hormone that is secreted thyroid gland. Thyroxin plays a major role in determining the metabolic rate of an individual. That is how much energy the body will use.

When the thyroid gland does not make adequate thyroxin this condition is known as hypothyroidism. In this condition due to less production of the thyroxin hormone the metabolic rate of an individual falls. There is inadequate utilization of the consumed macronutrients, thus there is a deposition of excess macronutrients in the form of glycogen in liver and muscle, muscle protein, and excess triglycerides in adipose tissues, which results in weight gain.

Whereas in hyperthyroidism there is hypersecretion of thyroxin which leads to an increase in metabolic rate and causes excessive depletion of body storages, like- glycogen, adipose tissues, and muscle protein, which results in a skinny appearance because of reduced body weight and excessive hunger.

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Role of Insulin

Insulin is a hormone that acts as a medium to a long-term regulator of our body weight through their action to decrease food intake and increase energy expenditure, ensure that energy expenditure and energy intake should be balanced.

Insulin acts at the CNS and peripheral nervous system to regulate food intake and acting on the periphery by influencing the storage of incoming nutrients. Hence, insulin involved in the synthesis and storage of fat.

Insulin also has an indirect effect on maintaining body weight by stimulating leptin. Impaired thermogenesis may happen due to impaired insulin activity. 

Insulin released and circulated in the bloodstream is proportionate to body fat content. Whereas increased insulin secretion is protective against weight gain in humans. Leptin production is stimulated by insulin, which acts centrally to reduce energy intake and increase energy expenditure.

Secretion and circulation levels of insulin in the bloodstream influenced by the amount and type of foods eaten, with decreased concentrations noted during fasting or energy-restricted diet. Insulin resistance is much more common among obese patients, also it may be associated with lack of response by insulin receptors, impaired glucose intolerance, and associated hyperlipidemia. This situation may be corrected by following a healthy diet and losing weight gradually.

Role of Glucagon

The alpha cells of the pancreas secrete this hormone. The primary role of glucagon is to maintain the blood glucose level when blood glucose level falls too low by signaling the body to release stored glucose.

Glucagon also plays an important role in controlling food consumption and the satiety feeling by signaling the body to reduce levels of other hormones responsible for increasing appetite like ghrelin.

In the case of obese individuals, glucagon cannot induce the feeling of satiety and doesn't suppress appetite.

Glucagon also helps to break down the stored form of energy like glycogen in the liver, fat in adipose tissue, and protein in muscle, hence helping to maintain healthy body weight or help in weight loss.