While nutrition experts know that eating the right kinds of dietary fat is key to a healthier lifestyle, some consumers still fear fats when trying to lose weight. Helping your clients understand how fat fits into their diet may help them achieve their weight loss goals while also improving other health parameters, such as lowering cholesterol.
According to a study published in the Journal of the American Heart Association, a diet containing unsaturated fats, such as those found in walnuts and olive oil, may have similar effects on weight loss as compared to a lower fat, higher carbohydrate diet1. Interestingly this study shows that a diet containing walnuts also positively impacts heart health markers, while also achieving weight loss.
“One of the surprising findings of this study was that even though walnuts are higher in fat and calories, the walnut-rich diet was associated with the same degree of weight loss as a lower fat diet,” said Dr. Rock, lead researcher from the University of California, San Diego School of Medicine.
The researchers studied 245 overweight and obese women (22-72 years old) enrolled in a one-year behavioral weight loss intervention. Participants were randomly assigned to three different diets: 1) a lower-fat, higher-carbohydrate diet, 2) a lower-carbohydrate, higher-fat diet, or 3) a walnut-rich, higher-fat, lower-carbohydrate diet, with guidance to reduce energy intake by 500-1000 calories per day. Those prescribed to a walnut-rich diet consumed 1.5 ounces per day. Looking at data from the first six months of the intervention, this study found that the average weight loss was nearly eight percent of initial weight for all groups.
According to the study, women who ate a walnut-rich diet saw comparable weight loss to the other study groups, however, they exhibited the most improvement in lipid levels, especially in those who were insulin-resistant. In addition to a significant decrease in LDL cholesterol, the walnut participants achieved a greater increase in HDL cholesterol as compared to the other diet groups.
Those enrolled in the lower-carbohydrate, higher-fat diet were encouraged to consume foods higher in monounsaturated fats, whereas the walnut-rich diet provided more polyunsaturated fats. Walnuts are the only nut in which the fat is primarily polyunsaturated fat (13g/oz.), including a significant amount of alpha-linolenic acid (ALA), the plant-based form of omega-3 fatty acids (2.5g/oz.).
Research on the benefits of polyunsaturated fats continues to grow. A recent Harvard study suggests that replacing saturated fats specifically with polyunsaturated fats and carbohydrates from whole grain is associated with a lower risk of heart disease.2 Additionally, the 2015-2020 Dietary Guidelines for Americans recommend consumption of polyunsaturated fats as a replacement for saturated fats3.
There are some study limitations that should be considered. The sample only included 245 women, so these results may not be generalizable to men. Although 245 participants were enrolled, the sample sizes for comparisons were reduced because the participants were divided into subgroups. In addition, there is a lack of detailed information about dietary intake and adherence to the diets. Considering the weight loss that was seen in participants, it seems that most were adhering to a reduced energydiet.
In addition to these findings, the researchers hope to explore the effect of walnuts on satiety, another critical factor in weight loss.
Resources:
1 Le T, Flatt SW, Rock CL, et al. Effects of Diet Composition and Insulin Resistance Status on Plasma Lipid Levels in a Weight Loss Intervention in Women [published online ahead of print January 25, 2016]. J Am Heart Assoc. doi: 10.1161/JAHA.115.002771.
2 Li Y, Hruby A, Bernstein AM, Hu FB, et al. Saturated fat as compared to unsaturated fats and sources of carbohydrates in relation to risk of coronary heart disease: A prospective cohort study. J Am Coll Cardiol. 2015;66(14):1538–1548. doi: 10.1016/j.jacc.2015.07.055.
3 U.S. Department of Health and Human Services and U.S. Department of Agriculture. 2015 – 2020 Dietary Guidelines for Americans. 8th Edition. December 2015. Available at http://health.gov/dietaryguidelines/2015/guidelines/