Losing sleep over not losing weight despite spending that extra half an hour in the gym? Following the calorie count prescribed by your dietician but still clinging onto those fat folds in your lower abdomen? Blame it on your metabolic rate and its slow decline over the recent decades. Researchers have found out that the human metabolic rate ( Basal Metabolic Rate) has slowed down in the last 30 years, literally paving the way for the global prevalence of obesity.
The energy spent by our body at rest for physiological functions is called the Basal Energy Expenditure (BEE) or the Basal Metabolic Rate. Activity Expenditure Energy (AEE) is the energy spent by the body while carrying out physical activities like exercise. The Total Energy Expenditure (TEE) of an individual is the total count of calories burnt during physical (AEE) and physiological activities (BEE).
“We calculated the Basal Energy Expenditure (BEE) or Basal Metabolic Rate (BMR) and have found that it has been on the decline since the last three decades. It could be one of the main factors responsible,” says Prof Dr Anura V Kurpad, Department of Physiology, St John’s Medical College and co-corresponding author of the study published in March 2023 edition of Nature Journal.
Essentially, a slow BMR means you will have to work out a lot more and eat a lot less to burn extra calories and maintain a healthy body weight.
“The total energy expenditure of an individual or the calories burnt should ideally be more than the calories consumed through food. If we eat or consume more calories than what our body burns, the excess calories get stored as fat and end up making you obese,” says Dr Kurpad.
Dr Kurpad explains that the researchers based their calculations on multiple factors, one of them being the amount of heat produced and oxygen consumption while the body is at rest.
Basal Metabolic Rate (BMR) and Dietary patterns
A main reason cited for the decline in BMR is the dietary pattern in which there are sharp variations in carbohydrates and fat intake with protein consumption being constant.
“Multiple factors influence BMR, including diet. Dietary changes during the obesity epidemic have included many things such as changes in the amounts of fiber and fat,” says the study.
The study also states that carbohydrates intake peaked in the late 90s and the fat intake has increased linearly since the early part of the 90s. The composition of fat also changed from saturated fats to polyunsaturated fats.
Dr Kurpad also states that the change in refined carbohydrate consumption (mainly from ultra processed food) as other factors are responsible for decline in the metabolic rate.
“Apart from diet, environmental factors like pollution including high particulate matter (PM2.5) in air, lead content in water and plastic in food, all have a role to play in this”. Dr Kurpad says. Increased screen time and decreased physical activity are also listed as possible reasons.
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The World Health Organisation and the Food and Agriculture Organisation (FAO) have charted out detailed energy expenditure rates for people of various age groups and body weight based on their energy intake, spent, body weight and metabolic rates. It is used as the basis for finding the energy requirements and suggesting nutritional plans for various populations across the globe.
“But the catch is that the majority of them depend on the WHO formula, which is based on data collected from Europe, mainly from army recruits in Italy,” Dr Kurpad says.
Caucasians (westerners) generally have more muscle mass than Asians, especially Indians. Indians are more predisposed to body fat which also puts them at high risk for various conditions including diabetes.
“So, the problem is Asians will tend to have more fat than muscle compared to westerners. The BEE will be higher in people with more muscles as it would produce more heat than the ones with extra fat since fat is inert,” Dr Kurpad adds.
The 10 percent variation in calorie count
Dr Kurpad says that an Asian with the same body weight as a western will not burn as many calories because of the excess fat stored in the body. He pointed out that the studies conducted on Indian people revealed that the BEE energy rate would be 10 percent less than the value arrived through the WHO equation.
“So if a European weighing 60 kg needs 1500 calories as per the WHO calculations, then an Indian with the same body weight will require 10 percent less (1350 calories). But this is not done and more calories get prescribed,” Dr Kurpad says. He also points out that it will further decline your BMR in the long run.
The holy grail for weight loss according to Dr Kurpad is, ‘Always eat at home, always eat less’.
Takeaways
Researchers have concluded that the metabolic rate has been on the decline for the last 30 years and one of the main reasons for the growing global pandemic of obesity. Multiple factors are being cited as the reasons for this slump, but dietary changes in recent decades, especially the increase in refined carbohydrate rich junk food and saturated fat rich animal meat could have a crucial role in it.
