Will eating nuts make me gain weight?

A large review of studies found that eating a handful of nuts every day did not lead to weight gain and in fact suggests that eating nuts may actually help prevent gaining excess body fat.Didyk/Getty Images/iStockphoto

If you avoid eating nuts because you’re afraid they will make you gain weight, consider rethinking your diet decision.

Nuts are calorie-dense due to their high fat content – one half-cup of peanuts, for instance, delivers 444 calories – but new research suggests the worry over nuts and weight gain is undeserved.

The large review of studies, published last month in the journal Obesity Reviews, found that eating a handful of nuts every day, which is recommended for heart health, did not lead to weight gain. What’s more, the findings suggest that eating nuts may actually help prevent gaining excess body fat.

About the study

The study, a collaboration between researchers from Canada and Spain, pooled the data from six observational studies and 86 randomized trials that had investigated the association between nut intake and weight gain and/or measures of body fat.

Many types of nuts – almonds, Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pine nuts, pistachios, walnuts and peanuts – were included in the studies.

Among the observational studies, a higher nut intake was tied to a reduced risk of overweight and obesity, as well as a lower likelihood of having an elevated waist circumference (e.g., 31.5 inches or greater for women and 37 inches or greater for men).

When the researchers pooled results from the randomized controlled trials, they found no evidence that daily nut consumption caused weight gain or increased waist size. The analysis showed that higher daily intakes of nuts was associated with reductions in body weight and body fat.

Protective effects of nuts

There are a few possible reasons why eating nuts may protect against weight gain. For starters, they’re a good source of fibre and protein, dietary components that promote satiety. A handful of nuts satisfies you faster, and for longer, than less-filling snacks like crackers and pretzels do.

The act of chewing nuts to break them down into pieces small enough to swallow also contributes to satiety by activating gut hormones that influence appetite.

As well, we don’t absorb all of the fat in nuts, which is contained within cell walls that are hard to digest. As a result, our bodies don’t ever see those fat calories. The researchers pointed out that the calorie content of nuts may be overestimated by 16 to 25 per cent, depending on the type of nut.

Weight aside, a regular intake of nuts is associated with other important health benefits such as guarding against type 2 diabetes, heart attack, stroke and death from cardiovascular disease.

Eating a handful of nuts each day has been shown to improve how the body uses insulin, enhance blood vessel function and lower LDL (bad) blood cholesterol and blood pressure.

How much? Which type of nuts?

The Mediterranean, DASH (Dietary Approaches to Stop Hypertension) and Portfolio diets recommend regular nut consumption. (The Portfolio diet is a plant-based eating plan that combines four cholesterol-lowering foods, including nuts, which are eaten daily.)

One serving of nuts is considered 1 to 1.5 ounces (28 to 42.5 grams). An ounce of nuts is equivalent to 23 almonds, 6 Brazil nuts, 18 cashews, 19 pecan halves, 11 macadamia nuts, 14 walnut halves, 49 pistachios or 35 peanuts.

All types of nuts provide heart-healthy unsaturated fats, calcium, magnesium, potassium, B vitamins and vitamin E. With the exception of Brazil nuts and macadamias, nuts also contain flavonoids, phytochemicals that deliver antioxidant and anti-inflammatory benefits.

Instead of sticking with just one type, include a variety of nuts to your diet to reap a wide range of their nutritional benefits.

One ounce of walnuts, for instance, provides 2.5 g of alpha linolenic acid (ALA); women and men need 1.1 and 1.6 g of this omega-3 fatty acid per day, respectively.

An ounce of almonds supplies half a day’s worth of vitamin E, an antioxidant that helps shield brain cell membranes and immune cells from free radical damage.

And Brazil nuts are an exceptional source of selenium, a mineral needed for proper thyroid function. If you eat these nuts every day, limit yourself to four to prevent consuming too much selenium.

Besides snacking out of hand, add nuts to stir-fries, fold them into whole grain pilafs, toss into green salads and sprinkle them over hot cereal or yogurt.

Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan. Follow her on Twitter @LeslieBeckRD

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