3. Not all fats are created equal Still, don't use your body's fat needs as an excuse to inhale every chocolate chip cookie or slice of bacon that crosses your path. "There are different types of fat molecules, and some are far better for you than others," says Mo. An easy way to tell the difference? "Bad" fats (saturated and trans fats) are usually found in animal-based and processed foods (think steak, cheese, butter, and doughnuts), while "good" fats (poly- and monounsaturated ones) tend to come from fish and plant sources, such as salmon, olive and soybean oils, nuts, and seeds.

So what's so harmful about saturated and trans fats? Put simply, they wreak havoc on the heart by raising the level of artery-clogging LDL cholesterol in your bloodstream. Trans fats also lower the amount of good-for-you HDL cholesterol, which helps clear those blood vessels of plaque buildup. In fact, one Harvard study found that for every 5 percent increase in total calories from saturated fat a woman consumes, her risk of heart disease jumps by 17 percent. Good fats, on the other hand, can have the opposite effect—a woman's odds drop by 42 percent for every 5 percent increase in unsaturated fat.

That's why experts advise getting nearly all your fat calories from unsaturated fats; less than 10 percent should come from saturated fat and less than 1 percent from trans fat. To curb your intake of these artery cloggers, opt for protein sources containing good fats, such as beans and fish, or ones low in saturated fat, such as pork, chicken, and lowfat dairy. You should also also choose lean red meat—round, sirloin, and top loin. Finally, read nutrition labels on processed foods and pick ones with the least amount of saturated fat and zero grams of trans fat per serving.