4. Eat less fast food

Here's yet another proof that fast food isn't exactly the most diet-friendly food around: A study by the University of Minnesota found that people who ate fast food more than twice a week gained an extra 10 pounds over 15 years, compared with people who ate fast food less than once a week. Fast foods are notoriously high in saturated fat and sodium, which not only lead to weight gain, but also elevate your risks of health problems such as diabetes and heart disease.

5. Cut back on refined carbs

According to recent findings published by the American Journal of Epidemiology, it's not the amount, but the kind of carbohydrates you consume, that triggers weight gain. Contrary to popular belief, overweight people don't eat more carbs than normal-weight individuals, but nutrition researchers found that they are more inclined to eat an excess of refined carbs.

Refined carbohydrates are, for example, those found in sugar, white bread, white rice, white bread, pasta and cereals. Meals and snacks that are laden with refined carbs have a high glycemic index, meaning they quickly break down into sugar, causing insulin levels to skyrocket and blood sugar to spike. If this blood sugar is not used by the body, it is stored as fat.

Replace refined carbs with unrefined carbs (wholemeal bread, whole wheat pasta, oats, veggies) and protein (lean meat) in your diet -- these nutrients break down more slowly, so you'll stay fuller for longer.