Walnuts are predominantly made up of good fats, which play an important role in the diet. The Dietary Guidelines for Americans recommends shifting food choices from those high in saturated fats to those high in good unsaturated fats, like those found in walnuts.
Walnuts can also be part of a healthy diet that won’t contribute to weight gain or hinder weight loss goals. Incorporating them into meals and snacks is a simple and convenient way to add important nutrients to your diet.
Walnuts can be eaten as part of a healthy diet that won’t contribute to weight gain or hinder weight loss goals.
While there are many factors that contribute to body weight, such as age, gender, genetics, and exercise, what we choose to eat is one aspect that can be modified to help achieve weight goals. With nearly 9-10 people being concerned about consuming dietary fat, the link between dietary fat and body fat still causes confusion.
Eating walnuts provides you with the types of good, unsaturated fats that are recommended by the Dietary Guidelines for Americans as a replacement for saturated fat (one ounce of walnuts contains 2.5g of monounsaturated fat and 13g of polyunsaturated fat, including 2.5g of omega-3 ALA). Walnuts can be eaten as part of a healthy diet that won’t contribute to weight gain or hinder weight loss goals. Below are study results from recent publications that demonstrate the role of walnuts in weight.
- Research from the Walnuts and Healthy Aging Study (WAHA), the first large study to explore the role of walnuts in healthy aging, found that walnuts could be incorporated into the daily diet of healthy older people without leading to weight gain. 1 This two-year trial included 365 healthy adults (average age 69 years) who were randomly assigned to either a diet with or without walnuts. The walnut group received 28, 42, or 56 grams (1, 1.5, or 2 oz) of walnuts per day to include in their typical diets. The amount of walnuts varied based on the individuals’ daily energy needs and the number of calories consumed in the walnut group were higher, on average, than the control group. Despite that, both the walnut group and control group saw comparable weight loss and a slight increase in body fat. Lean body mass, waist circumference, and waist-to-hip ratio remained essentially unchanged.
- Another study found that a diet containing unsaturated fats, such as those found in walnuts, may have similar effects on weight loss as compared to a lower fat, higher carbohydrate diet.2 Two hundred forty-five overweight and obese women (ages 22-72) were enrolled in a one-year behavioral weight loss intervention and randomly assigned to three different diets: a lower fat, higher carbohydrate diet (excluded nuts), a lower carbohydrate, higher fat diet (excluded nuts), or a walnut-rich (1.5 oz per day), higher fat, lower carbohydrate diet.
Both of these trials found similar weight loss whether walnuts were included in the diet or not, demonstrating that walnuts may be included in an overall healthy diet without having adverse effects on weight. Since these studies were conducted in older adults and women, larger studies in more diverse populations are needed to understand population-wide effects.
There are specific hormones and areas of the brain that tell the body if it’s hungry or full, which play a role in body weight. Research investigating appetite hormones and using novel brain imaging technology to explore neurological responses to food cues show promise for walnuts’ potential role. Below are two published research studies on this topic.
- A study in healthy adults (ages 18-35) who regularly consumed foods that contain polyunsaturated fatty acids (PUFA) experienced favorable changes in appetite hormones associated with hunger and satiety.3 Twenty-six participants consumed test meals high in saturated fat at the beginning of the study and then were placed on a seven-day control diet consisting of a typical American eating pattern or a diet high in PUFAs (included whole foods such as walnuts, Alaska salmon, tuna, flaxseed oil, grapeseed oil, canola oil, and fish oil supplements). After the seven-day diet, participants consumed meals high in saturated fat, again. Study participants that consumed a PUFA-rich diet had a significant decrease in fasting ghrelin, a hormone that increases hunger, and a significant increase in peptide YY (PYY), a hormone that increases fullness or satiety.
- Another study used magnetic resonance imaging (MRI) to explore possible connections between walnut consumption and central nervous system responses.4 Researchers found that consuming walnuts may activate an area in the brain associated with controlling hunger and cravings. Ten obese adult participants (ages 48-54) lived at the medical center for two 5-day sessions and were closely monitored for food intake and appetite. Participants reported feeling fuller when they consumed a daily smoothie with 48 grams of walnuts (approximately 1.7 ounces), compared to when they consumed a placebo smoothie with the same macronutrient content but with safflower oil instead of walnuts.
For both of these studies, larger and longer-term research is needed to clarify population-wide effects and determine the optimal intake of dietary PUFAs that offers the greatest health benefit.
Calorie Content of Walnuts
When monitoring body weight, being mindful of calories is also an important factor. Research from the USDA found that one serving of walnuts (one ounce) may provide 146 calories, which is 39 calories less or 21 percent fewer, than the 185 calories listed in the USDA Nutrient Database.5 The study takes into account the digestibility of walnut pieces and halves, and further research is needed to better understand the results of the study and how this technique for calculating calories could potentially affect the calorie count of other foods.
Walnuts can play an important role in helping you achieve or sustain your health goals. Try incorporating them into meals and snacks for a simple and convenient way to add important nutrients to your diet.
- 1 Bitok E, Rajaram S, Jaceldo-Siegl K, et al. Effects of Long-Term Walnut Supplementation on Body Weight in Free-Living Elderly: Results of a Randomized Controlled Trial. Nutrients. 2018;18:10(9).
- 2 Rock CL, Flatt SW, Pakiz B, et al. Effects of diet composition on weight loss, metabolic factors and biomarkers in a 1-year weight loss intervention in obese women examined by baseline insulin resistance status. Metabolism. 2016;65(11):1605-13.
- 3 Stevenson JL, Paton CM, Cooper JA. Hunger and satiety responses to high-fat meals after high polyunsaturated fat diet: a randomized trial. Nutrition. DOI: http://dx.doi.org/10.1016/j.nut.2017.03.008.
- 4 Farr OM, Tuccinardi D, Upadhyay J, et al. Walnut consumption increases activation of the insula to highly desirable food cues: A randomized, double-blind, placebo-controlled, cross-over fMRI study. Diabetes Obes Metab. 2018;20(1):173-177.
- 5 Baer DJ, Gebauer SK, Novotny JA. Walnuts consumed by healthy adults provide fewer available calories than predicted by the atwater factors. J Nutr. 2016;146(1):9-13.