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Once you finish reading this article you might realise that everything that you learnt about weight loss and hunger all this while was wrong. It is true that there is a connection between the brain and the gut that controls all physiological functions of the body and also promotes weight loss and satiety. Experts are still deciphering new facts about the same.
The hormones secreted by the brain in many ways are responsible for helping you lose weight, prevent overeating and burn calories. There is a unique way in which the brain and the gut work in tandem and help you lose weight. Here Dr Harsh Sheth, Digestive Health Institute, Mumbai explores the complexities of the gut-brain axis and how it influences weight loss.
What is the gut-brain axis?
The gut-brain axis is one complex inter-connection of the brain and intestine, which allows a two-way communication between them. This translates into the intestines being able to send signals to the brain about various things like satiety, sugar, mood, etc. The hormones released by the brain in turn influence other organ systems in the body to help start and shut down functions of the gut in a manner to control weight, diabetes, bowel movement etc.
How does the gut-brain axis help in weight loss and weight gain?
There are two hormones leptin and ghrelin produced in the intestine which helps the brain to know when to trigger a hunger response and when the body is satiated. Leptin is a hormone released by the fat cells, stomach, muscles and various other cells in the body. It is commonly known as the 'satiety hormone' and is almost the opposite of Ghrelin the 'hunger hormone'. Leptin is released by the body in response to an adequate meal and fat storage that is when you had a scrumptious meal and start feeling full. It also plays a crucial role in the regulation of body weight and energy balance. It circulates in the blood and binds to the receptors in the brain which produces a feeling of satiety or fullness.
This is when the brain realises that one is feeling full and receives the signal to stop eating more to pile up excess calories. It was previously thought that leptin levels would be low in obese patients, leading to a lack of satiety, over-eating and hence promote the state of obesity. However, subsequent research uncovered there is significantly elevated levels of leptin even in obese patients. These patients have a voracious appetite and a tendency to store fat, despite elevated leptin levels. So an obese person keeps feeling hungry, eats more and piles up calories but is never satiated.
Does that mean that the gut-brain axis in obese patients is distorted?
Yes, to an extent. This proved that some patients develop a state of leptin resistance, wherein the receptors in the brain somehow are unable to sense leptin and hence can't carry out its function. Leptin therapy with drugs is helpful in only a fraction of obese patients with low or absent levels of circulating leptin. Drug therapy doesn't help everyone to get the hormones work adequately to lose weight. Such patients are usually obese since childhood, due to a mutation in the genes encoding the hormone. This is when an extremely obese person is asked to go under the knife or do a bariatric surgery.
Is bariatric surgery the only answer for obese patients who are trying to lose weight?
No, a proper screening is done before selecting a patient for bariatric surgery. Not all obese patients suffer from leptin resistance. Leptin ideally limits adipose tissue accumulation, hence regulates body weight. At the same time, it also signals the brain to increase the energy expenditure to regulate the levels of adipose tissue in the body. In most cases, a strict diet and exercise regime can help one shed the pounds slowly and steadily. However, if it isn't happening and one still remains obese then a bariatric surgery is suggested.
Leptin levels are screened in all obese children, adolescents and adults, who are being worked up for bariatric/metabolic surgery. This helps to identify if obesity is due to either leptin deficiency monozygous obesity (usually seen in infants and children) or leptin resistance (usually seen in adolescents and adults). This serves as a guide for treatment options and helps select the patients for different forms of intervention -- medical management or bariatric/metabolic surgery.
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