I recently posted a study about almonds, how an ounce of raw whole almonds may contain 14 grams of fat, but only 1 gram of that fat (8.5%) is freed for absorption by chewing. You could almost consider whole almonds a low-fat food.
This next study found that cooking liberates fat in a manner similar to chewing or grinding, maybe better:
Cooking Increases Net Energy Gain From A Lipid-Rich Food, American Journal of Physical Anthropology, January 2015
The lipid-rich food here was peanuts. Researchers fed mice one of four diets that included peanuts: raw and whole, raw and blended, roasted and whole, and roasted and blended.
The two on the right, the roasted ones, provided a lot more fat and calories than the two on the left:
Our findings indicate that cooking increases the fraction of lipid available and the net energy gained from peanuts.
Mice that ate the roasted peanuts weighed significantly more than mice that ate the raw peanuts. The raw-eaters excreted more fat in their feces. Out it went. Even though they chewed the nuts well. In fact, the mice chewed so well that the authors surmise the whole nuts “were effectively blended upon reaching the stomach and small intestine.”
The same cannot be said for humans:
Prior studies have noted that human subjects given peanut butter (peanuts that have been roasted, and then ground) excreted less fat than those given whole roasted peanuts. This implies that mechanical processing of cooked peanuts increases the digestibility of their lipid, and presumably the energy gained from them.
Mice, it seems, are little chewing machines. “[Their] masseteric extension helps rodents produce large bite forces that favor high chewing efficiency.”
Here are a few more bits from their lit review which support the notion that the less processed a nut is (the less cooked, the less ground), the fewer calories we derive from it:
Adults consuming diets supplemented with raw, whole nuts achieve similar weight loss outcomes as those consuming non-supplemented control diets, despite the additional calories (Casas-Agustench et al., 2011).
Consumption of a roasted peanut paste promotes rapid weight restoration in malnourished children (Ashworth, 2006)
So … raw almonds provide such little fat they could be considered part of a weight-loss plan, but peanut butter provides so much fat and so many calories you’d only want to eat it if you’re trying to gain weight. As I’ve been saying for years now, calories listed in tables are ballpark numbers. Note that NutritionData continues to list calories and fat in raw peanuts the same as in roasted peanuts: