Nuts are reportedly chock full of all kinds of nutrients and are probably among the healthiest of snacks. However, they are also among the most calorie-dense foods – a small handful of nuts (~30 g) can easily add up to 150-200 cals.
So, do high consumers of nuts run the risk of weight gain?
This issue is discussed in depth by Sze Yen Tan and colleagues in a paper published in the American Journal of Clinical Nutrition, in which they review the effects of nuts on appetite, food intake, metabolism, and body weight.
While eating nuts may not exactly lead to weight loss, most studies find that consumption of “extra” calories as nuts leads to substantially less weight gain than may be expected based on their caloric content.
Their review reflect a number of ways in which nuts may have this effect:
Effect on hunger and appetite:
“…nut ingestion suppresses hunger and desire to eat and promotes fullness. These sensations may aid dietary compensation that offsets much of the energy contributed by nuts. However, strong compensation can also occur independently of reported appetitive effects. This may reflect imprecision in appetite measurement or a truly independent uncharacterized mechanism.”
“Nuts require considerable oral processing effort and this may, in part, account for the often-noted less-than-predicted effect of their consumption on body weight. The mechanical act of chewing reportedly generates satiation signals through cognitive, neural, endocrine, and physical (eg, gastric emptying) mechanisms; augments cephalic phase responses linked to appetite; influences digestion efficiency; modestly increases energy expenditure; and elicits dietary compensation.”
“A number of studies have evaluated the efficiency of energy absorption from ground and tree nuts through feeding trials. All showed substantive increases in fecal fat loss with nut consumption, although the values ranged widely from ∼5% to >20%”
“Collectively, there is some evidence that nut consumption increases thermogenesis, but the data are not robust and there is no clear mechanism. One possibility is that the lipid from nuts is absorbed over a prolonged period of time, leading to a small but sustained source of substrate that fuels thermogenesis and could appear as an increase in REE.”
“It has been proposed that nut consumption elevates fat oxidation and preferentially reduces body fat mass, especially in the viscera. These actions are attributed to their high unsaturated fat content….Human studies incorporating different nuts into the diet at realistic doses are needed to determine the effect of nut consumption on body composition.”
With regard to impact on body weight, the authors reach the following conclusions:
Adding nuts to habitual diets:
“Although there are reports of small, but significant increases in body weight with nut consumption, the preponderance of evidence indicates that under controlled or free-living situations, nut consumption does not promote weight gain.”
Eating nuts in calorie-restricted diets:
“The inclusion of nuts in energy-restriction regimens does not impede weight loss. In several trials in which nuts did not augment weight loss, there was a reduction in cardiovascular disease risk indexes in the nut-consuming groups, suggesting that such benefits derive from properties of the nuts rather than just weight change.”
Eating nuts in weight maintenance:
“Several studies assessing the role of nut consumption in weight-maintenance programs have noted a decrease in body weight from baseline. Whether this is due to a greater thermic effect of food or REE effect of the nuts compared with the foods they displaced in the diet has not been established. Nevertheless, current data indicate that the inclusion of nuts in a weight-maintenance program will not lead to weight gain and may aid weight loss.”
Thus, in summary, the authors conclude that,
“…evidence indicates that they pose little challenge to and may even aid weight management. This is attributable to the strong dietary compensation effects they elicit, inefficiency in the absorption of the energy they provide, and possibly an elevation of energy expenditure and fat oxidation.”
As a general caveat to all of these data, it needs to be noted that results varied widely depending on the types of nuts and how exactly these nuts were consumed (e.g. as snacks or added to meals – the former often being more favourable than the latter).
Also, many of the studies had relatively small number of participants and were of rather short duration.
Nevertheless, it does appear that going nuts about nuts may not be quite as detrimental to your weight as their energy content would suggest.
Tan SY, Dhillon J, & Mattes RD (2014). A review of the effects of nuts on appetite, food intake, metabolism, and body weight. The American journal of clinical nutrition, 100 (Supplement 1) PMID: 24920033