Nuts have been said to provide numerous health benefits, including lower risk of heart disease. However, its ability to help prevent metabolic disorders and obesity remains disputed.
This led researchers at Wuhan University to conduct a meta-analysis to determine nut consumption’s link to obesity and metabolic syndrome.
Nuts about weight loss
They obtained eligible studies from PubMed and Embase, including six prospective cohort studies involving 420,890 participants and 62 randomised feeding trials involving 7,184 participants.
All the prospective cohort studies assessed participants’ nut intake using food frequency questionnaires, the most often adjusted factors were age, sex, physical activity, smoking, and alcohol and total calorie intake.
The clinical trials had a follow-up periods ranging from three weeks to almost 6.5 years.
They researchers then reported that the results of the randomised trials showed that nut consumption was associated with a significant decrease in body weight, BMI, and waist circumference.
Additionally, these results were consistent in the sensitivity analysis, with no publication bias detected.
The meta-analysis of the prospective cohort studies found that for every weekly single serving increase in nut intake, the risk of metabolic syndrome dropped by 4%, becoming overweight / obese by 3%, and obesity alone by 5%.
The pooled data of the clinical trials suggested that nut supplementation could reduce BMI, body weight, and waist circumference, “further supporting the metabolic benefits of nuts”.
Different types of nuts have been reported as having anti-obesity and anti-cardiovascular disease effects. According to a Chinese study, walnut consumption might lower heart disease risk by improving endothelial function.
An Australian study found that consuming foods rich in omega-6, such as nuts, could reduce the risk of type 2 diabetes.
Nuts, which are also high in fibre, have been found to help lower cholesterol and blood pressure, thereby reducing heart disease risk.
The science behind the seeds
The researchers behind the current study said there were a few possible reasons for these effects. High nut intake provides abundant bioactive compounds, including dietary fibre, plant protein, unsaturated fatty acids, antioxidants, vitamin E, phytosterols, and arginine, as well as minerals such as calcium, potassium and magnesium.
Individually or together, these nutrients may improve oxidative stress, inflammatory response and endothelial function, in turn reducing the risk of metabolic syndrome.
More recently, the gut microbiota has been highlighted as a vital component in the pathophysiological process of metabolic disease and obesity.
It is believed that non-bioaccessible substances from nuts — polysaccharides, fibre, and polymerised polyphenols — possess prebiotic properties, which result in positive changes in microbiome structure.
Other factors, such as enhanced satiety, increased resting energy expenditure, diet-induced thermogenesis, incomplete chewing, and fat malabsorption were also said to contribute to the weight-loss effects of nuts.
Additionally, participants who had consumed more nuts tended to eat less processed and red meats, which also helped to prevent metabolic syndrome and obesity, since such meats have been said to raise the risk of metabolic abnormalities.
In conclusion, the researchers wrote: “The results from this meta-analysis suggest that nut intake may be associated with decreased risks of metabolic syndrome and overweight / obesity, and lower body weight measures.
“The result supports the current recommendation of nut intake for the prevention of chronic diseases. Future prospective studies are still warranted to enhance our findings and to determine the health benefits of specific nuts.”
Source: Nutrition & Metabolism
“Nut consumption and risk of metabolic syndrome and overweight/obesity: a meta-analysis of prospective cohort studies and randomized trials”
Authors: Hang Li, et al.