Weight loss guidelines misleading — study
Unrealistic targets are being issued across UK due to failure to allow for changes to metabolism, scientists say
London National guidelines that advise people how to lose weight are seriously flawed and grossly overstate how quickly they will reach their targets, scientists say.
Researchers found people lost only half as much weight as expected in a year if they followed the advice given by the NHS and US health organisations.
The problem came to light when government scientists at the US National Institutes of Health in Maryland realised standard weight loss advice — including its own — failed to account for changes in metabolism as people lost weight.
The rule of thumb used by the NHS and other health services assumes that if a person cuts 500 calories from their daily diet, they will lose about 450gm each week, regardless of how long they adhered to the regime.
Further complicated
But as people lose weight, their metabolism slows until they reach a new stable body weight. Their weight loss is further complicated by how much body fat and muscle they have when they start dieting.
"Dietitians and physicians have used this rule of thumb for a long time, but it turns out to be completely wrong. It doesn't account for metabolic changes that happen when people change diet," said Kevin Hall, who led the research. "If you change calories, your metabolism slows down and eventually you reach a plateau."
He told the annual meeting of the American Association for the Advancement of Science: "If you want to lose 10lb of weight eventually, you need to cut 100 calories a day from your diet. You will get halfway there in a year, but then plateau after three years. The old rule of thumb predicts twice as much weight loss after a year and gets worse after that."
