The New York Times has an article on the latest out of the Nurses’ Health Study, Nurses’ Health Study II and the Health Professionals Follow-up Study. Some of the findings predictive of weight gain are in line with Paleo; others are not:
The foods that contributed to the greatest weight gain were not surprising. French fries led the list: Increased consumption of this food alone was linked to an average weight gain of 3.4 pounds in each four-year period. Other important contributors were potato chips (1.7 pounds), sugar-sweetened drinks (1 pound), red meats and processed meats (0.95 and 0.93 pound, respectively), other forms of potatoes (0.57 pound), sweets and desserts (0.41 pound), refined grains (0.39 pound), other fried foods (0.32 pound), 100-percent fruit juice (0.31 pound) and butter (0.3 pound).
Question 1: The only things that most of us would disagree with here are the red meats and the butter. Can we attribute these discrepancies to recall bias? Doesn't that taint all the other findings that we agree with (which, let's face it, are in the great majority). Maybe it's because they don't distinguish between grass fed and regular supermarket meat? Does that mean we should only eat red meat if we can afford grass fed? But why the butter?
They also enumerated what, according to the study, leads to weight loss:
Also not too surprising were most of the foods that resulted in weight loss or no gain when consumed in greater amounts during the study: fruits, vegetables and whole grains. Compared with those who gained the most weight, participants in the Nurses’ Health Study who lost weight consumed 3.1 more servings of vegetables each day.
They also mention that yogurt and nuts are associated with long-term weight loss.
Question 2: Here, we would all agree with the veggies and some of us would agree with moderate fruit intake. But whole grains? I know they're marginally better than refined grains, but still.
On the whole, I think most of these results are in line with Paleo, which is refreshing and somewhat surprising. However, I can't seem to figure out why increased butter and red meat intake is associated with weight gain, while whole grains are associated with weight loss. My initial thought is that people who choose to eat whole grains over refined grains do so mostly to lead "healthy" (albeit SAD) lives; therefore, in other aspects of their lives they would also choose healthier behaviors that could confound the findings (e.g. they floss, they choose to take the stairs more often, etc...all those little factors that go unmeasured but that could add up to a big protective effect).
Since this is Harvard, they did of course adjust for the usual: physical activity, smoking, etc. Here's a link to the abstract.