Fats often come with a bad reputation. Our on-going obsession with low-fat foods doesn't help either. But contrary to popular opinion, not all fats are evil. In fact, your body needs fats to work properly, says nutritional therapist Sally Duffin, who has a BSc in Nutritional Medicine. "Fats are important for things like keeping energy levels stable, helping skin to stay supple, improving the condition of your hair and nails, keeping joints flexible, eye and brain health, hormone regulation and healing wounds." The key, she adds, is to focus on the good fats and eliminate the bad fats in your diet.

Bad fats

These are the fats you should cut back on as they increase cholesterol levels and your risk factor for stroke, heart disease and other conditions:

Saturated fats come from mostly animal-based foods (think fatty red meat, cheese, butter and whole fat dairy products), explains Duffin. Some plant-based oils also contain saturated fat, including palm kernel, palm, and coconut. Saturated fats can form plaques that build up in the blood vessels, increasing the risk of clogged arteries and cardiovascular diseases.

Trans fats are fats that have been chemically altered -- using a process called hydrogenation -- so that they solidify and have a longer shelf life. This transformation, however, made trans fats rigid. "They make cell membranes rigid and disrupt the ability of nutrients to get into cells," warns Duffin. In fact, experts believe that trans fats are worse than saturated fats, and should be avoided as much as possible. Trans fats are typically found in many processed and packaged foods such as cookies, crackers and cakes. You can spot them by looking for the words "partially hydrogenated" and "hydrogenated" in the ingredient list.

Good fats

Unlike the bad fats, these fats actually help your heart health. They can lower cholesterol and reduce your risk of heart disease:

Monounsaturated and polyunsaturated fats are the main examples of good fat. Olive oil, sunflower oil, peanut oil, sesame oil and avocado are good sources of monounsaturated fat.

Polyunsaturated fats include omega-3 and omega-6 fatty acids -- they're both essential, meaning our body cannot make them and you have to get them from food. Rich sources include soybean oil, walnuts, sunflower seeds, pumpkin seeds, fatty fish and tofu.

Moderation is key

So how much good fat should you aim to eat? The key is moderation, says Duffin. That's because all fats -- whether they're good or bad -- have nine calories per gram. So if you overindulge, it will still add to your waistline. The American Heart Association recommends:

• Limiting fat to 25-35 percent of total daily calories.
• Limiting saturated fats to less than 7 percent of your total calories. Meaning, if you're eating 2,000 calories a day, less than 140 calories (16 grams) should come from saturated fats.
• Limiting trans fats to less than 1 percent of your total daily calories.