A new U.S. study adds to growing evidence that nuts - once considered too fattening to be healthy - may in fact help keep weight down, in addition to offering other health benefits.

Researchers found that study participants who ate the most tree nuts - such as almonds, Brazil nuts, pistachios and walnuts - were between 37 and 46 percent less likely to be obese than those who ate the fewest tree nuts.

People who ate the most nuts were also less likely to have a suite of risk factors known as metabolic syndrome, which is tied to increased risk of heart disease and diabetes.

"This is another study that shows there is an association between eating nuts and not being obese and having less tendency to have metabolic syndrome," Dr. Joan Sabaté told Reuters Health.

Sabaté is the study's senior author from Loma Linda University in California.

The study, which was published online in PLOS ONE, was partially funded through a grant from the International Tree Nut Council Nutrition Research and Education Foundation (INC NREF).

In another recent study, also funded by INC NREF, researchers found that people who reported eating the most nuts were less likely to die over a 24-year period than those who ate the fewest nuts.

While such evidence can't show that nuts cause the differences seen between people who love them and those who pass them by, there are reasons to believe nuts provide a direct benefit, Sabaté said.

For example, nuts are high in unsaturated fat, which is known as a "good" fat compared to the saturated fat found in animal products. The high protein content of nuts may also lead people to feel fuller and eat less unhealthy foods. They also contain of host of other nutrients and plant chemicals that are beneficial to health, Sabaté said.

For the new study, the researchers used data on the diets of 803 Seventh-day Adventist men and women in the U.S. who were already enrolled in another study.

Overall, those who ate a lot of tree nuts - about 16 grams (half an ounce) per day - were just a little over normal weight, on average, compared to those who ate few or no nuts and were seriously overweight or obese.

A normal body mass index (BMI) - a measure of weight in relation to height - for an adult falls between 18.5 and 24.9, according to the U.S. Centers for Disease Control and Prevention. Overweight people have BMIs between 25 and 29.9 and a BMI of 30 or more is considered obese.

People in the study who ate the most nuts averaged BMIs of about 27 while those who ate the least - less than 5 grams of tree nuts per day - averaged BMIs of 29 to 30.

The researchers also found that one third of the participants in the study had metabolic syndrome, which is defined as having three or more conditions associated with heart disease and diabetes risk. (Those include being obese, having high blood pressure and high cholesterol, and having a large waistline).

For every one-ounce serving of tree nuts consumed per week, however, a person's risk of having metabolic syndrome dropped by 7 percent.

Jeffrey Blumberg, a professor of nutrition at Tufts University in Boston who was not involved in the new research, said it is consistent with a number of previous studies showing that including nuts in one's diet is beneficial.

"It really is at a point now where I think there is a large body of evidence and is - I would even say - a consensus of nuts being a healthful food choice if consumed in reasonable amounts," Blumberg said.