Replacing saturated fat in your diet, found largely in meat and dairy, with unsaturated fat, found in foods such as avocados, nuts, and fish, is regarded as better for your cardiovascular health. But consuming a lot of fat of any type can easily lead to eating excess calories, and thus weight gain. (One gram of fat contains 9 calories, compared with 4 calories per grain each for carbohydrate and protein.) The latest dietary guidelines from the government recommend adults get 20 to 35 percent of total calories from fat.
Source: Consumer Reports on Health November 2014