It’s a commonplace reason given for weight gain and a subsequent inability to lose it. As a consequence there are queues at the doctor’s to check for an underactive thyroid!
But there are a number of rational reasons why this weight gain theory is clearly an obesity red herring.
- Weight excess was far less prevalent 50 years ago. If we are to assume that slow metabolisms are the cause of a sudden increase then we have to accept the unlikely possibility that a human evolutionary change is taking place across the world at miraculous speed.
- The distinction between energy that we use to stay alive (metabolism) and energy used through our daily activities is an artificial one and the boundaries are a bit blurred. The combination of both categories represents our total energy expenditure and again, 50 years ago, irrespective of vocation, build, height, age, gender we were much better at matching our calorie input to output. There’s no set amount we need to consume. It’s just a case of matching our consumption to our expenditure. If it were true that someone only used up a total of 500 calories a day they would be less hungry than the rest of us and they just wouldn’t need very much to eat!
- Our metabolism includes our heart and respiratory functions, digestion, brain function, body temperature and cell maintenance, and these tasks carry on largely unnoticed all the time. All that work needs lots of energy. I would invite anyone to explain which aspect of metabolism could slow without the individual affected being aware of it. And even if it could actually occur, with or without awareness, surely appetite would reduce accordingly to compensate? Losing weight is already extremely difficult and building unnecessary barriers is not going to help.