Interesting study that looked at the energy from nuts (David J Baer Sarah K Gebauer Janet A Novotny. Walnuts Consumed by Healthy Adults Provide Less Available Energy than Predicted by the Atwater Factors. The Journal of Nutrition, Volume 146, Issue 1, 1 January 2016, Pages 9–13).
Results: One 28-g serving of walnuts contained 146 kcal (5.22 kcal/g), 39 kcal/serving less than the calculated value of 185 kcal/serving (6.61 kcal/g). The ME of the walnuts was 21% less than that predicted by the Atwater factors (P < 0.0001).
Conclusion: Consistent with other tree nuts, Atwater factors overestimate the metabolizable energy value of walnuts. These results could help explain the observations that consumers of nuts do not gain excessive weight and could improve the accuracy of food labeling.
This may explain why I weigh nuts and don’t seem to get the weight increase that the raw calories would indicate.
Similar results for another type of nut ( Baer DJ, Gebauer SK, Novotny JA. Measured energy value of pistachios in the human diet. Br J Nutr. 2012 Jan;107(1):120-5.). In that case the difference is less at about 5%.
Don’t take this as license to eat big bags of nuts. It’s only 20% for walnuts.