Potatoes appear not to cause fat gain, and in fact frequently cause fat loss and improve metabolic health in people who are overweight. The Washington Potato Commissioner Chris Voigt illustrated this in his two month potato-only diet, during which he lost 20 lbs and greatly improved his metabolic and cardiovascular biomarkers without feeling hungry. I interviewed Mr. Voigt and gave my thoughts in a series of posts (4, 5). Some people objected that Mr. Voigt may not have been impartial since he had an interest in making potatoes look good. Although my gut feeling was always that he was being straightforward about his experience, it's nevertheless a reasonable concern.
This year, a fascinating thread appeared in the Mark's Daily Apple forum. Apparently inspired by an exchange with Ray Cronise, someone decided to go on a potato diet and began losing weight rapidly (6). The thread snowballed as other people joined in and found that they were also losing weight rapidly on the potato diet (potatoes, sometimes with a small amount of added fat). It is worth noting that most of these people were coming from a primal-style low-carbohydrate diet*. As of right now, the thread has 104 pages.
People have proposed explanations for this phenomenon, and some have been amusing, such as the attempt to explain the effect via the insulin-obesity hypothesis.
Those of you who followed my writing on food reward and "why we eat" will understand that fat loss is exactly what one would expect from a diet like this, and in fact the diet echoes the recommendations I published in 2011 for using food reward as a fat loss tool (7). The potato diet works because:
- Potatoes have a low calorie density and a high satiety value per calorie.
- Eating a diet that is composed almost exclusively of one food is low in reward, low-moderate palatability, low in variety, and has a high sensory-specific satiety. Even if you dress up your potatoes as well as you can, you're still eating potatoes. This tends to reduce calorie intake.
- Potatoes are nutritious enough (including complete protein) that they can be the sole source of calories for an extended period of time. However, they are not a complete source of all micronutrients and deficiencies will eventually arise.
* For the record, I'm not implying that the Primal Blueprint or other reduced-carbohydrate Paleo type approaches are fattening. It is a fact that PB and similar approaches have helped many people lose fat and become healthier, and will continue to do so.