However, consuming monounsaturated fat -- nuts, avocados, olive oil, flaxseed oil, grape seed oil -- can be good for the heart, a University of Montreal researcher said.

"Research on animals and some clinical trials show that not all fats have the same effect on weight," Nadiah Moussavi, a graduate student from the University of Montreal said in a statement.

Using statistics from the U.N. World Health Organization, Moussavi studied the prevalence of obesity in women age 15 and older. The study found that in the countries where monounsaturated fats, such as found in olive oil, formed an integral part of the diet, no or few people were found to be overweight.

Countries where the obesity rate was high and the consumption of monounsaturated fat low included Saudi Arabia, Egypt and Peru. Countries such as France, Denmark and Italy showed an ideal portrait -- low rates of obesity with a high consumption of mono-unsaturated fats, Moussavi said.

Thirty-eight percent U.S. women were obese and ate 152.2 grams of fat daily, of which 45.9 grams were monounsaturated.

Moussavi said family history, amount of exercise, consumption of fruit and vegetables also play a role.

"Our study shows that the consumption of mono-unsaturated fats and maybe other fats also play a role," Moussavi said in a statement.