Eating one serving of beans, peas, lentils or chickpeas every day may help dieters lose a little extra weight, according to a new analysis of existing research.
Researchers examined data from nearly two dozen trials and found that participants who ate about three quarters of a cup of legumes every day lost about three quarters of a pound more than those who didn't eat legumes, regardless of whether the diets were geared to weight loss.
Lead author Dr. Russell de Souza told Reuters Health that legumes - or pulses, as they are known in many parts of the world - are an important sustainable protein source, plus they're high in fiber.
"Legumes also have a low 'glycemic index,' which means the carbohydrates in them do not raise blood sugars as rapidly as things like white bread or white flour," said de Souza, a researcher with the Li Ka Shing Knowledge Institute of St. Michael's Hospital in Toronto.
Previous studies have found that eating foods high in fiber and protein and low in the glycemic index promote weight loss, but the specific role of legumes hasn't been clear, de Souza and his coauthors write in The American Journal of Clinical Nutrition.
"We did this study as one in (a) series of papers we are working on to assess the effects of pulses on blood pressure, blood cholesterol, body weight, and appetite control to help guidelines committees to better formulate dietary advice," he said by email.
The researchers culled 19 studies, based on 21 clinical trials that compared the effects of diets containing legumes with diets that didn't include legumes, but had the same number of calories.
Only four of the studies were designed as weight loss studies; the remainder were meant to study weight-maintainance. A total of 940 obese or overweight adults participated in the trials, which lasted from four to 12 weeks.
After an average of six weeks, the study participants who ate legumes every day lost about 0.34 kilograms (0.75 lb) more than those who didn't.
"Though the amount of weight loss was small, it's important to state that the pulse-containing diets we reviewed were not designed for weight loss," de Souza said.
Six of the trials also suggested that eating legumes was linked to slightly lower body fat, though there was no evidence of a difference in waist circumference.
De Souza said swapping legumes for other sources of protein, such as meat, may be a painless way to eat healthier and lose a little weight.
"In another study we did, we found they may help with appetite control - eating 100 calories worth of pulses at a meal will make you feel about one-third more full than 100 calories from another food," he said.
De Souza said that losing weight is relatively easy - but keeping it off is much, much harder.
"This is where eating more pulses in your daily diet can really help, we think," he said.
There were some limitations to the study. Many of the trials were short-term and not of the highest quality. The authors also couldn't tell what the long term effects of eating legumes would be.
Lauren Graf, a registered dietitian with Montefiore Medical Center in New York, said she wasn't surprised by the findings and that there are multiple health benefits to eating legumes regularly.
"Beans are loaded with antioxidants and phytochemicals that help protect against cancer and cardiovascular disease," Graf, who was not involved in the study, told Reuters Health by email.
The fiber in legumes helps lower levels of LDL (bad) cholesterol in the blood, Graf said.
For people who are not accustomed to eating beans, adding about a half cup per day is a good place to start, she said, adding that they can be used in place of other starches like potatoes or rice.
Graf also suggests adding cooked lentils to salads and to homemade veggie burgers, or incorporating them into soups and stews.