A while back I wrote an article about peanuts addressing if there was any legitimacy to the canonical paleo-diet view that they are harmful and should not be eaten. Long-story short, no, and I discussed numerous studies documenting the ability of peanut consumption to help regulate blood sugar, blood lipids, and satiety. Additionally, I talked about a relatively new type of peanut created through 30 years of selective breeding that is much higher in monounsaturated fatty acids (MUFAs) and lower in polyunsaturated fatty acids (PUFAs) than the conventional peanut.

As it turns out, this “high-oleic” (HO) variety is the primary peanut grown in Australia, and Barbour et al recently published a study investigating what happens when you take a bunch of otherwise healthy overweight-obese adults who don’t regularly consume nuts and have them start eating 2-3 ounces of HO peanuts per day without any other dietary advice.

Ultimately, 61 participants completed this 12-week randomized crossover trial. Roasted, unsalted HO peanuts with skins on were provided in 28 g sealed foil packets by the Peanut Company of Australia. Males were provided with 3 packets (84 g) per day and females 2 packets (56 g) per day to be consumed for 6 days per week (to assist with compliance subjects were given one rest day per week with no peanuts). However, because people don’t like doing what they are told, actual daily peanut intake was about 67 and 48 g/day for males and females, respectively.

Weighted food logs showed that consumption of HO peanuts increased energy intake by about 10% (220 kcal), which was attributed to a 23 g (~30%) increase in intake of fat that was almost entirely MUFA (22 g increase). There was also a 9% increase in protein intake and 15% increase in fiber. However, the amount of calories supplied by the peanuts averaged 330 kcal per day, indicating that some compensation must have occurred. Because carbohydrate intake was relatively unchanged, it is likely that the peanuts were eaten in place of other fatty foods, despite the overall increase in fat consumption.

Confirming the increased caloric intake, a small but significant increase in weight was observed (+0.5 kg), but this was only 26% of the increase that could be expected based on the increase in caloric consumption (~1.9 kg). Additionally, body mass per calorie consumed was significantly less (~11%) on the peanut diet compared to the habitual no-nut diet, suggesting that the participants were able to eat more calories at a given body weight. Finally, MUFA intake significantly correlated with reductions in body fat.

Previous research has found that fecal fat and energy losses are greater with whole peanuts compared to peanut butter, oil, or flour and this may be owed to the fact that the fat is trapped within walled cellular structures which may not be completely broken down upon chewing. Moreover, MUFAs are oxidized more easily than long-chained saturated fatty acids (SFAs) and previous work has shown increased fat oxidation in overweight-obese adults with the consumption of HO peanuts vs conventional peanuts. Perhaps a combination of reduced fat absorption and increased fat oxidation contributed to the less than predicted weight gain with additional energy intake.

Despite the small increase in weight and the increased caloric intake, there were no changes in inflammation, blood lipids, glucose metabolism, insulin resistance, or β-cell function.

This study shows that adding ~330 kcal of HO peanuts into the habitual diets of overweight-obese men and women has little to no impact on numerous cardiometabolic risk factors and leads to significantly less weight gain than expected based on caloric intake. It may be that a combination of increased MUFA intake and incomplete fat absorption played a role in these outcomes, but whatever the reason, it is clear that HO peanuts have a strong satiety effect and can be safely incorporated into the diet as a means to increase protein, fiber, and MUFA intake.