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Rapid weight changes linked to cancer

by Ed Yong | Analysis

24 July 2007

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Crash diets may be doing us more harm than good. That’s what a new study on body weight and kidney cancer seems to suggest.

The problem with the vast majority of diets is that they just don’t work in the long term.

True, we might temporarily lose enough weight to look good in that swimsuit, but after a bit of time, most people just put the weight back on. And when it comes back, the lost weight often brings reinforcements with it.

You might think that losing and gaining weight in this way wouldn’t be too bad. But a group of American and Swedish scientists think differently.

They did a study of over 140,000 American women and looked at how their weight changed over several years.

  • At the end of the study, they found that women whose weight went up and down many times had higher risks of kidney cancer.
  • To be exact, if their weight went up and down by 10 pounds, for more than 10 times over the course of the study, their kidney cancer risk went up by 2.6 times. That’s a pretty hefty increase in risk!
  • Just one a note of caution – even though the study was very large, only 269 women (out of the several thousand involved) developed kidney cancer. That’s a relatively small number as far as these studies go.

So the results can’t be treated as gospel, but they do make sense in light of what we know about obesity and cancer.

Many other studies have firmly established that having too much weight can cause several cancers, and kidney cancer is one of these. (And this study confirmed that women with a higher waist-to-hip ratio had a higher risk of kidney cancer).

So, there’s a lot of evidence that our bodyweight influences our cancer risk, but if crash dieting doesn’t work, what should we do?

In 2006, Cancer Research UK launched the Ten Top Tips programme, together with the charity Weight Concern.

The tips are designed to help you make long-term changes to your daily routine, the best way of losing weight and keeping it off. All of the tips are all based on scientific evidence.

Given that the majority of diets are less-than-effective, why not give them a try?