Scientists have been trying for years now to understand what causes overweight and obesity in some but not in others. Now researchers at the Monash University's Biomedicine Discovery Institute seem to have solved the puzzle that has been baffling them all – a so called “fat switch” in the brain that regulates weight gain. This could also mean a new potential for treatment of obesity in future. The study appeared in the journal Cell Metabolism today.
Researchers from the Metabolic Disease and Obesity Program working in their laboratory looked at adipocytes or fat cells in the body. These are special cells that can change into one of the two forms – white fat and brown fat. White fat stores energy and brown fat makes the energy ready for use. Feeding has a way to control the white fat into brown fat and thus making it available for use. This is termed “browning of the fat.
This study went on to show that after eating, the brain gets into action. It signals the release of insulin the levels of which start to rise after a meal as the blood glucose levels shoot up. The brain then signals the adipocytes to change the stored white fat cells to brown fat so that the body can expend energy. But long hours of fasting has an opposite effect – the brain tells the brown fat to be converted to white fat so that it can be stored for future use. Both of these processes help the body to maintain the body weight and prevent excess weight gain or loss in response to fasting and feasting. So with time the body weight tends to remain stable.
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This new study has found that there is a switch like mechanism in the brain that can help sense insulin in the body and coordinate the next feeding accordingly. This switch controls the browning of the fat. After fasting this switch prevents the browning to conserve the energy by turning on. Similarly, after feeding the switch is off and it promotes browning of fat. Lead researcher Professor Tony Tiganis explained that in obesity this switch remains on and does not turn off. This makes the fat more white than brown. Switching off the browning means that energy is continuously being stored and not spent and this storage leads to weight gain said Professor Tiganis.
According to first author of this study Dr Garron Dodd the “missing piece of this puzzle” was why the brain was turning off the switch to promote browning. That it was turning white fat to brown was earlier known after a series of research in 2015. According to him, this study is “exciting” because it shows why this phenomenon occurs as well as what is the underlying mechanism.
Next step, say researchers would be to explore if this switch in the brain could be turned off from outside using it as a therapy target in obesity. This could promote loss of the excess weight. Professor Tiganis emphasized the importance of this study saying that obesity brings a huge disease burden worldwide and may lead to “falls in overall life expectancy”.
This study was supported by Australian National Health and Medical Research Council.
Obesity and overweight
According to the World Health Organization (WHO), obesity has doubled since 1980 and in 2014 an estimated 1.9 billion adults were overweight and 600 million of these were obese. Further 41 million children below 5 years of age globally are obese. Obesity is one of the most preventable of all non-communicable diseases.
Overweight and obesity means higher body mass index or BMI. Body mass index (BMI) is a simple index of weight-for-height defined as weight in kilograms divided by the square of his or her height in meters (kg/m2).
For adults, WHO defines overweight and obesity as follows -
- Overweight - BMI greater than or equal to 25; and
- Obesity - BMI greater than or equal to 30.
Statistics show that obesity and overweight is related to more deaths globally than malnutrition or being underweight. Except in sub-Saharan Africa and Asia, the number of obese and overweight in a population exceeds underweight. The main reason for gaining weight is an energy imbalance – excess calories consumed and too few spent in physical activity. Changes in dietary and physical activity patterns have been blamed for this rising epidemic of overweight and obesity.
Being overweight or obese is linked to several ailments including cardiovascular diseases (mainly heart disease and stroke), type 2 diabetes, diseases of the muscles, bones and joints such as osteoarthritis, several cancers such as breast, endometrium, ovarian, liver, gall bladder, colon, and kidney and prostrate.
This burden of obesity may be reduced by supportive environments for lifestyle changes. Healthier food choices, more awareness and motivation regarding regular physical exercise and activities can help ease this burden.