An Interview With Keri Glassman. Glassman, a nutritionist based in New York City, is the author of The Snack Factor Diet.

A lot of people know that snacking on nutritious food helps you avoid overeating by curbing cravings, but research shows that eating the right way between meals can also improve your mood and help you stay sharp.

Don’t snack hungry. Rate your hunger on a scale from one to ten, ten being famished. Have a snack when you’re at a six (slightly hungry) and stop when you’re at a four (slightly satisfied). This ensures that you’ll eat a controlled amount. If you’re too hungry when you snack, you’re much more likely to overdo it.

Choose your snacks wisely. Make your snack as nutrient-dense as possible, and limit it to 150 calories. Look for foods that are high in fiber, lean protein, or unsaturated fat, like cottage cheese with fresh fruit, half an apple with peanut butter, or a couple of high-fiber crackers with almond butter.

Whenever possible, choose fresh foods such as fruits, vegetables, and nuts, which tend to have more nutrients and fewer preservatives than packaged food. Snacks that have a lot of sugar or starchy carbohydrates (candy or potato chips, for example) will give you a quick burst of energy, but then you’ll crash and end up feeling even more lethargic after. [source: Allure]