Do hormones cause weight gain?

 

As summer approaches, the war with flesh begins again.  But unfortunately, it fails every time.  How is appetite controlled that makes dieting so difficult?  If you know the hormones related to obesity, energy balance, appetite and satiety, you can understand a little bit of why.

obesity, energy balance

“Obesity” refers to an excessive accumulation of adipose tissue in the body.  If the body obesity index (BMI, kg/m2, normal 18.5 to 25) is 25 or more, it is said to be overweight. However, if you have a lot of muscle mass and a little fat, it doesn't apply.  In addition, the dispersion of fat is also important.

Central obesity and visceral obesity accumulated in the trunk or abdominal cavity are more dangerous than fat accumulation in the subcutaneous tissue.  Obesity begins with excessive food intake due to disruption of energy balance and abnormal control of appetite and satiety.

Hormones and nerves are closely involved in ‘regulation of energy balance’.  A number of hormones produced by fat cells, stomach, ileum and colon, and pancreas produce afferent signals.  Afferent hormones are processed and integrated in the hypothalamus arcuate nucleus to produce an “efferent” signal.

Different signals regulate food intake and energy expenditure, respectively, along two metabolic pathways: synthesis and degradation.  ‘POMC/CART neurons’ in the hypothalamic arch nucleus drive weight loss through energy expenditure and decreased appetite.

Conversely, NPY/AgRP neurons promote food intake and weight gain.  It is also associated with the secretion of melanin-concentrating hormone (MCH) and orexin, which stimulate appetite.

appetite and hormones

‘Appetite and satiety’ is a kind of afferent system that transmits signals to the central nervous system.  Representative hormones involved are 'leptin', 'adiponectin', and 'gut hormone' secreted by the gastrointestinal tract.

Leptin is a hormone that is synthesised in fat cells and leads to weight loss.  It stimulates appetite-suppressing POMC/CART neurons and inhibits appetite-inducing NPY/AgRP neurons.

Leptin is involved not only in appetite, but also in energy expenditure, such as physical activity and heat production.  Loss-of-function mutations in the leptin family may indicate severe obesity.

Adiponectin is known as a fat-burning molecule.  It oxidises fatty acids in the muscle and shows the effect of reducing fat mass.  In addition, it reduces the influx of fatty acids into the liver and reduces the total amount of triglycerides (TG), thereby protecting glucose-related insulin sensitivity.

‘Guest hormones’ usually act on the short-term initiation and termination of meals, and include ghrelin, PYY, and amylin.  Ghrelin is produced in the stomach and hypothalamus to stimulate NPY/AgRP neurons to ingest food.  PYY is secreted in the ileum and colon and acts as an appetite suppressant.

Amylin is a peptide hormone secreted along with insulin by pancreatic β cells.  It is evaluated as a treatment for obesity and diabetes because it reduces food intake and weight gain.  PYY and amylin stimulate POMC/CART neurons to reduce food intake.

Obesity is unavoidable if 'secretional dysfunction' or 'genetic inactivation' occurs in leptin, adiponectin, and gut hormone, which are involved in appetite and satiety.  Obesity and appetite are also closely related to 'genetics and family history'.

Let's carefully check the lifestyle, body type, and obesity level of family and friends.  There is no need to resent what you are born with.  There may also be healthy obesity.  But, somehow, obesity is not beneficial.

As mentioned above, there are many complex processes associated with obesity, but the simplest way to reduce obesity is to reduce energy input and increase physical activity.  Control the amount and composition of food and exercise.  Remember, it is “eat less and move more”.