Saturday, September 12, 2009

Low-Fat Diet Disaster

Saturated fat has historically been the "number one enemy" of dietitians and nutritionists. For decades, popular thought was that the most effective way to lose weight or to prevent weight gain was to eat a diet low in fat. This approach to weight loss and management has had disastrous consequences; however, because of its subsequent timing with the explosion of refined carbohydrates (as opposed to whole grain foods) and sugary beverages.

Indeed, there is little, if no, evidence that eating a diet low in fat will result in weight loss in the long-term. We discussed eating patterns, such as a low-fat diet, in a class I am taking this semester on Obesity Epidemiology with Frank Hu, author of the book by the same title.  In it, he reviews the most current research on the causes of obesity and the health consequences of obesity. Oh, and you thought obesity was itself a disease.

While a low-fat diet, per se is not going to be a great population strategy for curbing the obesity epidemic it does seem that fat may affect those with a genetic predisposition to obesity differently than those without one (this was a study of Swedish women). Therefore, a low-fat diet may work as a weight loss strategy for some people; for example, if obesity runs in your family.

Further, "not all fats are created equal," Hu said in class yesterday. This is especially true when in comes to trans fat; as at least one nine-year follow-up study in a cohort of US men showed that increasing consumption of trans fat (but not other types of fat) led to greater waist circumference. The findings held, even after the authors adjusted for changes in BMI over time.

The low-fat diet movement illustrates the difficulty of promoting a universal public health message for diet and nutrition that is both simple, and is evidence-based. A low-fat diet paints the picture that all fat is bad; which can lead to disastrous eating patterns. People may avoid using olive oil or butter, but show no hesitation about consuming the partially hydrogenated oil in their crackers or breads. Similarly, it gives no indication as to what should be properly substituted for fats. For most Americans, it appears they took out fats and replaced that with sugar-sweetened beverages, high-fructose corn syrup, refined carbohydrates, and were left with a diet completely void of fiber and other health promoting nutrients.

Fat is an important part of our diet. The key is to use fat wisely.

If you think you are doing yourself a favor by choosing that 80 calorie non-fat yogurt with aspartame and chemical additives, think again. If you think you are being healthy by using non-fat salad dressing with nearly double the amount of high-fructose corn syrup or sugar, think again.

Trans fat is the enemy of nutritionists today (saturated fat still seems the enemy for some). However, fats in their most natural form -- from olives, nuts, seeds, meats, avocados! -- should be embraced.


Kelsey Woodruff said...

I've always thought the "non-fat" movement was strange when foods either substitute sugar or chemicals for natural fats. Does our body convert sugar into fat? Sugar is, of course, an addiction of mine. But I refuse to eat non-fat yogurts because they taste like chemicals. I'd rather have 1% milk fat that tastes like milk and contains less chemicals. Likewise, I'd rather use a tiny bit of real butter on my bread than loads of chemicals that cause the fake butter to be spreadable.

Katelyn Mack said...

Kelsey, Thanks so much for your comment. You definitely make a great point: most non-fat foods are able to mimic the taste of full- or low-fat alternatives because of additives, including sugars or other thickeners/stabilizers.

I learned today that even skim milk has added protein in it because when they take out all the fat the milk becomes blue! I guess they figure people probably wouldn't eat blue milk so they add proteins, which might be implicated in some chronic diseases, including certain cancers (because of its link to growth-promoting hormones). Yikes!

Now if we could just resist those breakfast or after dinner treats!