Increasing walnut consumption by just half a serving (14 g) a day can help alleviate the gradual increase in weight usually during adulthood and contribute to prevent obesity, a new study in the journal said. BMJ Nutrition, Prevention and Health.
Nuts are high-fat foods rich in unsaturated fatty acids, vitamins, minerals and fiber. Their high fat content leads some to consider nuts unhealthy and to avoid those trying to manage or lose weight.
The consumption of nuts and seeds in the US increased from 0.5 servings / day in 1999 to 0.75 servings / day in 2012.
Research team led by Dr Dedder Tobias of Harvard TJ University The Jan School of Public Health aims to assess the association between changes in total walnut consumption and intake of different nuts (including peanuts) and long-term weight change, in three independent group studies.
They analyzed information on weight, diet, and physical activity in 51,529 male health workers (40-75 years) from the Health Care Study; 127,700 nurses (35-55 years) of the NHS Study; and 11,6686 nurses (aged 24-44) from the Nursing Study II (NHS II).
Over 20 years of monitoring, participants were asked to indicate their weight every 4 years, and how often they ate a serving (28 g) of walnuts, including peanuts and peanut butter during the previous year.
The average weekly exercise – hiking, jogging, cycling, swimming, rocket sports and gardening – was assessed every two years by a questionnaire. It was measured in the metabolic equivalent of working hours, which express how much energy (calories) is consumed per hour of physical activity.
The average annual weight gain in all three groups was 0.32 kg.
Between 1986 and 2010, total nut consumption increased from a quarter to just under half a serving / day in men; and from 0.15 to 0.31 servings / day in women in the NHS study.
Between 1991 and 2011, total daily nut consumption increased from 0.07 to 0.31 servings for women in the NHS II study.
Increased consumption of any kind of nuts was associated with less long-term weight gain and less risk of becoming obese (BMI of 30 or more kg / m2), overall.
Increasing walnut consumption by half a serving a day was associated with a lower risk of putting on 2 kg or more over any 4-year period. And, the daily half of an increase in the consumption of nuts is associated with a 15% lower risk of obesity.
Replacing processed meat, refined grains or desserts, including chocolates, cookies, pies and donuts, for half a serving of nuts was associated with maintaining weight between 0.41 and 0.70 kg at any time of 4 years.
Within any 4-year period, supplementation of daily walnut consumption by no-one to at least half the gate was associated with preservation of a weight of 0.74 kg, lower risk of moderate weight gain and 16% lower risk of obesity , compared to not eating nuts.
A consistently higher walnut intake of at least half a serving per day was associated with a 23% lower risk of putting on 5 kg or more and becoming obese over the same time frame. No such associations have been observed to increase peanut butter intake.
"Our findings support dietary recommendations for nutrition and support the incorporation of nuts as an effective strategy for making viable dietary modifications for primary obesity prevention," said Dr. Tobias and his colleagues.
X. Liu et al. 2019. Changes in walnut consumption affect long-term weight change in men and women in the United States. BMJ Nutrition, Prevention and Health, posted online 23.09.2019; doi: 10.1136 / bmjnph-2019-000034