We have some good news to share: no, eating fats does not automatically make you fat. Overeating any macronutrient (fat, protein, or carbs) increases the risk of weight gain, said registered dietitian Kristin Kirkpatrick at Cleveland Clinic Wellness, but "fat in and of itself is not something that will make you fat," despite the rather misleadingly identical terminology.
You can understand where the misconception comes from, though. "Fat can be a pretty scary nutrient" for those who count calories, Kristin said, because it's more calorie-dense: one gram of fat contains nine calories, compared to four calories per gram of protein and four calories per gram of carbohydrate. "People also may associate fat with more 'indulgent' foods, such as butter and steak," Kristin told POPSUGAR, adding to the misconception that all fats are unhealthy. Then there's the simple association that eating fats might simply create fat in the body, which isn't necessarily the case; you're likely to gain weight if you eat processed or unhealthy foods or overeat consistently, including fats, but fats don't inherently lead to weight gain.
In fact, Kristin said, many of her clients have been able to lose weight on high-fat diets, often because they replace refined carbs and sugars with healthy fats (snacking on nuts instead of pretzels, for example). The popular ketogenic diet, which is high-fat and low-carb, is one that has helped many people lose weight, although it's still controversial among dietitians.
According to Kristin, fats are also harder to digest than other nutrients, such as carbs. That means they take longer to move through your digestive system, which helps you stay full for longer and have fewer snacking cravings. Fats boost your metabolism for the same reason; your body needs more energy (aka burns more calories) to digest them.
How much fat should you eat, then? On average, aim to keep fats as 30 percent of your daily diet, though Kristin noted that this can vary based on your body, activity level, and general health; consult a doctor or dietitian for guidelines specific to your body. You should also stick to healthy fats as much as possible, including avocados, nuts, whole soy, olive oil, and fatty fish like tuna and salmon. (Check out this post on the healthiest sources of fats for more options.)
So no, you probably don't need go nonfat to lose weight or simply stay healthy. Keeping those healthy fat sources as a part of your regular diet, balanced with carbs and plenty of protein, is the best way to go. Here's a healthy, balanced two-week clean eating plan to get you started.