Nuts are packed with nutrition, but they are also packed with calories. Why, then, don't nuts seem to make people fat? In my video Nuts and Obesity: The Weight of Evidence, I profile a review published back in 2007 looking at about 20 clinical trials that had been done on nuts and weight. Not a single one showed the weight gain one would expect.
All of the studies either showed less weight gain than predicted, no weight gain at all, or actual weight loss--even after study subjects added a handful or two of nuts per day to their diet. However, the studies lasted just a few weeks or months. What about long-term?
Maybe in the short run nuts don't lead to weight gain as much as other foods, but what about after years of eating nuts? Well that's been examined six different ways in studies lasting up to eight years. One found no significant change and the other five out of six measures found significantly less weight gain and risk of abdominal obesity in those eating more nuts.
Since that review is now 5 years old, in my Weight of Evidence video I update it to include all of the studies published since, including a number published this year. For example, in 2012 there was study in which people added over a hundred pistachios to their daily diets for three months and didn't gain a pound. How did 30,000 calories disappear?
What happened to the missing calories? The mystery has been solved. In my video series that started with Solving the Mystery of the Missing Calories, I presented the "pistachio principle" and the fecal excretion theory. In my next video these theories were put to the test. I then explored the Dietary Compensation Theory, and by the final video in the series we had figured it out.
Part of the trick seemed to be that nuts boost fat burning within the body. But how? It could have something to do with the amino acid arginine (see my 2-min. video Fat Burning via Arginine) or the phytonutrients found in nuts and green tea (Fat Burning via Flavonoids).
-Michael Greger, M.D.
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