In the past there have been dramatically different views as to whether yo-yo dieting might affect your metabolism and make it difficult to lose weight and keep it off. A new study, carried out by researchers at the Fred Hutchinson Cancer Research Center in Seattle, has found that a history of repeatedly losing weight only to put it back on again doesn’t affect your metabolism. And that’s good news for the estimated 10 to 40 percent of the population of the Western world affected by yo-yo dieting.
“A history of unsuccessful weight loss should not dissuade an individual from future attempts to shed pounds or diminish the role of a healthy diet and regular physical activity in successful weight management,” said Anne McTiernan, MD PhD, a senior author of the study.
It looked at data from 439 overweight to obese sedentary women aged from 50 to 75. The women were randomly placed in four different groups. The first group was on a reduced-calories diet only, the second on exercise only (mainly brisk walking), the third was reduced-calorie diet plus exercise, while the fourth was the control group and continued their lives as normal. When the year-long study was over those women in the diet-only, and diet and exercise groups lost, on average, 10 percent of their starting weight.
The aim of the study was to find out whether it was more difficult for women who had experienced moderate to severe weight cycling dieting to lose weight, compared to women who hadn’t been yo-yo dieters in the past. Eighteen per cent (77 women) were classed as severe weight cycling dieters, saying they had lost 20lbs or more on three or more occasions. Twenty four percent of the women were classed as moderate weight cycling dieters, having lost at least 10lbs on three or more occasions.
The study found that there were no significant differences between the women who had been yo-yo dieters and those who hadn’t. When it came to their ability to take part in diet and/or exercise programmes, and the percentage of body fat and lean muscle mass lost or gained, they didn’t differ that much. The researchers also looked at other factors, including blood pressure, insulin sensitivity, and hormone levels, and found no noteworthy differences here either.
“We know that there’s an association between obesity, sedentary behaviour and increased risk of certain cancers,” said Anne McTiernan. “The World Health Organisation estimates that a quarter to a third of cancers could be prevented with maintenance of normal weight and keeping a physically active lifestyle.”
“It’s actually thought that about 17,000 cases each year in the UK are linked to overweight and obesity, and we may well find that this goes up, as more cancers are linked to overeating and obesity,” said Yinka Ebo, Senior Health Information Officer at Cancer Research UK.
“The best way to lose weight is to eat healthily, eat smaller amounts and become more active, rather than going for short-term fixes. Choose simple, small lifestyle changes, rather than fad diets.”
Why does weight matter?
According to the World Health Organisation, overweight and obesity come second only to smoking when it comes to preventable risks for cancer.
To give just a few statistics, between seven percent and 15 percent of breast cancer cases in developed countries are caused by obesity. Cancer Research UK has funded two major studies that found that obese women have a 30 percent higher risk of postmenopausal cancer than women who are a healthy weight.
Obesity is an important risk factor for bowel cancer. Two large studies have shown that obese men have about 50 percent higher risk of bowel cancer than healthy men. Obesity also increases the risk of womb cancer, oesophageal cancer and many other types of cancer.
And it doesn’t stop at cancer. Obesity is also a major risk factor for heart disease. Together with circulatory disease, heart disease is responsible for more than 191,000 deaths a year in the UK. Obesity is also clearly linked to diabetes.
British Heart Foundation
Cancer Research UK