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What’s metabolism got to do with weight gain, loss?

What’s metabolism got to do with weight gain, loss?

Experts say those with a slow metabolism burn fewer calories while their body is at rest -- and tend to gain weight easily
Photo by Goutham V

While some people do not put on weight despite gorging on heaps of junk food, there are others who gain kilos despite consciously choosing to eat healthy. What plays a major role in both the scenarios could be one’s body metabolism.

What is metabolism and why does it matter in weight management? Metabolism is the process through which the body converts food and liquids into energy that is then used to carry out basic body functions. From breathing and digesting food to repairing cells and managing hormone levels, metabolism provides the energy required to power several essential body functions. How fast or slow a person’s metabolism works depends on the genes they have inherited.

Explaining the process of metabolism, Dr Mahesh Chavan, consultant, endocrinology, Apollo Hospitals, Navi Mumbai, says, “There are hormones in our body that metabolize carbohydrates, proteins and fats. Every time a person eats a meal, it is broken down and while some of it gets converted into energy that is used for basal body functions, whatever remains of the carbohydrates, once the body is replenished, gets converted into fat.”

Edwina Raj, senior clinical dietician, Aster CMI hospital, Bengaluru, says those with a slow metabolism burn fewer calories while their body is at rest, and they tend to gain weight easily. “People with faster metabolism, though they eat junk food, don’t have the tendency to put on weight easily. That’s how metabolism matters in weight management,” says Raj.

Dr G Moinoddin, consultant, bariatric and advanced laparoscopic surgery, Manipal Hospitals, Miller Road, Bengaluru, says that weight gain/loss is multifactorial. “Cases where people eat a lot but still do not gain any weight could be due to multiple factors. Firstly, their inbuilt basal metabolic rate [the number of calories burnt for carrying out basic body functions while the body is at rest] can be very high, which means that their body ends up digesting everything they eat and there is no weight gain. Or some people may be suffering from hyperthyroidism, a condition where the thyroid functioning is more and the metabolism rate goes up and they digest everything and don’t gain weight,” he says.

Genetics and weight management

As per ‘The impact of genetic polymorphisms on weight regain after successful weight loss’, a study published in the British Journal of Nutrition, although weight regain after weight loss can be multifactorial, genes associated with eating behaviour, satiation and energy release were found to be linked to the ability of long-term weight maintenance.

Dr Moinoddin says there have been cases where he has operated upon six to seven obese members of the same family, which has made it evident that genes play a big role in weight management.

“In cases where people gain weight despite eating very less, firstly the genes could be the reason. If there is a history of obesity in the family, it will be transferred down to the kids. Similarly, if the familial genes are strong, the metabolism will be high. Among young women, who show up with weight gain despite eating very less, meanwhile, one of the reasons could be polycystic ovary syndrome. Hormonal changes play a major role in metabolism. Another reason could be hypothyroidism, a condition in which the thyroid functioning is less, metabolism slows down and they gain weight despite eating less.”


Raj says there are several tests available to check if a person’s genetic makeup and inbuilt metabolism rates are causing weight gain or loss.

“A DNA analysis can be done using their saliva sample,” she says. “We have seen many cases where people who come to us with weight gain have turned out to have a very slow metabolic rate as per their DNA tests. Apart from the DNA test, we also ask them to do a body composition analysis — to check their body fat, muscle mass and their metabolism — to understand what their resting metabolic rate is. This way we can precisely personalise and customise their nutrition prescription. The protein, calorie, carb and fibre intakes differ from one person to the other and only after a detailed analysis will we be able to fix their nutrient intake.”

Raj says that depending on a person’s genetic makeup, detailed DNA analysis and body composition analysis, a micronutrient intake plan is drawn up. “If we customise their nutrient intake based on the results of these tests, the outcome is more likely to be positive,” she says.

It was during one such detailed medical check-up at work that 28-year-old Allen Augustine from Kerala found that his metabolism rate was much faster than that of his colleagues. “My metabolic age, as per the test results, was much lower than my actual age. It was lower compared to the results of others of the same age as well. That’s when I understood that my metabolic rate is faster than those around me,” says Augustine, who adds that he has been lean all his life.

A 2019 study, ‘Younger Relative Metabolic Age Is Associated with a More Favorable Body Composition and Plant-based Dietary Pattern’, found that people with a lower relative metabolic age had significantly lower body weight, body mass index and consumed more grains and vegetable proteins while people with a higher relative metabolic age reported greater cravings for fat-rich foods and consumed greater amounts of pork and cold cuts/sausages.

“The basal metabolic rate or the rate at which a person’s metabolism is set, slows down as you grow older. When you’re young, your metabolism is high. When you’re middle-aged, your metabolism slows down,” says Dr Moinoddin.

Can your metabolic rate change?

“Those with a slow metabolism need not think that their metabolic rate can never change. Some clients take this as the reason for their weight gain or loss, assume that nothing can be done and give up. But that’s not the case,” says Raj.

Even certain types of food and exercise impact the body’s metabolism.

“Though we all have a genetic influence on our metabolism, it can be changed through exercise, physical activity and diet. There are certain types of food that we can introduce to their diets and lifestyle changes we can suggest to boost metabolism. In such cases, we generally introduce protein-rich foods. I have observed that people with low metabolism also tend to have lower muscle mass, which is co-related to low protein intake. Caffeine can also improve one’s metabolism,” she says.

A 2020 study, ‘A Critical Review on the Role of Food and Nutrition in the Energy Balance’, also found that caffeine increases the body’s energy expenditure.

Dr Moinoddin says sedentary habits and eating food at the wrong time also lowers one’s metabolism rate. “Breakfast should be heavy, and dinner should be very light,” he says. “It is advised that you eat a heavy breakfast because you need energy for the whole day. Heavy meals at night disturb the pancreas and disturb the insulin process, leading to weight gain.”

Raj says that people who gain or lose weight due to genetics and metabolism often lose their patience. “There should be complete compliance with the nutrition prescription and routine we recommend,” she says. “Most people lose patience and do not understand that weight management is a long-term commitment.”


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3 Responses

  1. Didn’t know metabolism rate was so critical. Is there any way to improve one’s metabolism?

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