Monday, December 18, 2006

The Skinny on Low Fat and Breast Cancer

It's because of headlines like this that I actually started writing this blog,

"Lower-fat diets cut breast cancer recurrence: Study".
They've been all over the net and newspapers over the course of the past few days, all because of a study that has followed 2,437 breast cancer survivors and compared those who followed a low-fat diet with those that didn't with regards to breast cancer recurrence.

The results, trumpeted loudly in the press, report that those with a lower fat diet had a 24% lower risk of breast cancer recurrence over a 7 year period.

Sounds great right? Low-fat must be the only way to go right?

Probably not.

It's not that a low-fat diet is a bad thing. It's not that I'm telling people not to follow low-fat approaches. It's just that the most likely reason for the reduction in recurrence in the low-fat group is the fact that the low-fat group lost weight.

Obesity and the risk of cancer is a very well established fact. The biggest study looking at cancer and obesity was conducted by Calle et al and published in the New England Journal of Medicine. The authors, after following over 900,000 men and women for over 16 years concluded that 20% of all cancer deaths in women were associated with overweight and obesity as were 14% of all cancer deaths in men.

To me, there's no doubt that there were some women in the control group (the non low-fat group) that also lost weight. I have no doubt because many women will take the diagnosis of breast cancer and use it to inspire them to live much healthier lives than before their diagnoses, improving their fitness, their dietary choices and quite often, their weights. Given that there is no formal in-paper comparison between low-fat weight losers' and regular fat weight losers' risks, and given that I'm by nature a highly suspicious guy, and given that an article stating that a low-fat diet reduces breast cancer recurrence risk is a much more exciting result than one that does not, I can't help but wonder if either the authors had those numbers and chose not to report the result that any way you lose weight is good, or if they purposely avoided crunching those numbers so as not to have to report them.

This argument wasn't lost on the American Cancer Society either, who in the press report I read specifically pointed out,
"that studies focusing on fat in the diet have not clearly shown this to be a breast cancer risk factor, although being overweight has been found to raise breast cancer risk, especially for women after menopause."
Clearly the argument wasn't lost on the authors of this study either as the last line of the Reuters piece reads,
"The researchers noted that women who ate less fat lost weight, and that the weight loss may have been at least partially responsible for lowering the relapse risk rather than the reduced fat intake alone."
So if you've had breast cancer should you go on a low-fat diet to improve your chances? Sure, but ONLY if you actually feel like you can live on that low-fat diet forever and more importantly ONLY if your low-fat diet leads you to lose weight.

Remember, weight loss has nothing to do with low-fat or low-carb. Weight loss has everything to do simply with lower calories, and whatever way works for you is good.

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2 comments:

  1. Anonymous8:40 am

    Linked to this old post through a chain of others...do you still believe that weight loss is all about calories? If I subsisted on one 1,600 calorie McDonald's meal or 1,600 calories worth of packages baked goods from the gas station market but still lost weight that would be "good"?

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  2. Weight management is about calories, and so yes, just like nutrition professor Mark Haub, if you eat 1,600 calories of gas station mart food, you can lose weight.

    The notion of "good" is relative.

    Nutritionally I'd argue the 1,600 McDonald's or gas station calories would pale in comparison with 1,600 calories of home made, from scratch, heavy on whole ingredients cooking.

    But yes, I'd expect you to lose roughly the same amount either way.

    I'm also not a slave to nutrition. If you felt you could manage your weight eating a dramatically less than ideal diet nutritionally, likely the benefit of your sustained weight loss would outweigh the nutritional risks of the diet required to get there.

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