That may be your walnuts, but not the variety that are near me (US), which are exactly like shown in his pictures. In fact, we have a tree just like that at my dad’s place, and I’ve never attempted to open the walnuts, as they are too hard.
It’s not that they are high calorie, it’s that they are high in PUFA. PUFA cause your fat cells to be insulin sensitive, meaning your fat cells are sucking up insulin and blood sugar. You’re getting fatter.
By contrast, saturated fat causes your fat cells to be insulin resistant, meaning they cease to take in insulin and blood sugar. You’re getting thinner.
Read the article again with this in mind. He has these points: (1) it’s hard to get a lot of calories for paleo man from the walnuts of the type near him; (2) we freak out about the PUFA differences between grass-fed and grain-fed steak, when you can get hundreds of times more PUFAs via nuts like walnuts; (3) PUFAs cause insulin sensitivity of your fat cells:
“We discussed how the FADH2:NADH ratio can be a switch flipping on a little insulin resistance. If the FADH2:NAHD ratio gets above a certain threshold, reverse electron transport takes place through Complex I in the mitochondria and produces a bit of superoxide, which drives a little local insulin resistance.”