By all accounts, the potato ought to be one of the most fattening natural foods around. It’s glycemic index value is as high as anything, which should spike your blood sugar and trigger an insulin and fat storage response. And yet a guy goes on a two-month potato diet, loses weight and seems to improve health in a couple of other respects too.

To add to that, folks over at the Weston Price Foundation and others have noted that there are traditional cultures around the world that have eaten massive amounts of potato without seeming to suffer from the “diseases of civilization” that plague the developed–and increasingly developing–worlds today.

So how do we reconcile this with the rather simplistic “carbs bad, fat and protein good” thinking that sometimes surfaces in the Paleo and low-carb communities?

One theory is that if (1) you don’t have a metabolism that has already been broken by eating the bags of sugar associated with the Standard American Diet (SAD); and (2) you continue to avoid the junk associated with the SAD, then you can eat decent quantities things like potatoes without weight gain or insanely high blood glucose levels. Those are some pretty big “ifs” for most Americans. It also helps if you are getting regular exercise that depletes muscle glycogen (again, a pretty big “if” for most Americans).

Glucose regulation is quite complex, varying from individual to individual and the overall content of their diet. Ideally, you’d test yourself for glucose intolerance post-meal, as described by Stephan Guyenet here to know what your tolerance level is for potato goodness.

In my own case, I base my potato consumption on activity levels. On weeks when I do a lot of riding, I increase the level of potatoes. On other weeks, such as this one where I’m recovering from a bike crash (and it’s raining anyway), I go fairly low carb. I think I might pick up a glucose meter just out of curiosity. I should add that my diet is otherwise pretty solid (mostly meat, eggs, veggies, and some dairy), and the last thing I need or want to do is lose weight.

Figuring out what works for you takes experimentation and adaptation based on your goals. Even if we start with our best thinking about evolutionary principles, there’s a lot of variation in the traditional diets that have kept people healthy across the world, and there is a lot of learning and study that needs to be done. That’s part of what keeps things interesting.