Fat is not only an essential nutrient, but it can also help you lose weight by filling you up and helping to satisfy cravings, Glassman says. In fact, she adds that a sensible diet is made up of about 30 percent fat. The key is choosing the right fats, and that can get a little confusing. "I have a lot of clients who are still afraid to eat nuts," Glassman says.
A better way to think about it: "Choose healthy (i.e., unsaturated or monosaturated) fats that come from nuts as well as avocado, fish, seeds (including flaxseed and chia seeds) and olive oil," Glassman says, and be mindful of portion size (for example, only a palmful of nuts). Limit your consumption of not-so-healthy saturated fats from cheese, butter, cream, fatty cuts of meat and palm oil. And avoid trans fats—commonly found in processed foods like chips, cookies and margarine—which, Glassman says, can not only cause weight gain but can also raise LDL ("bad") cholesterol and increase the risk of heart disease.