The average American makes more than 200 decisions about food every day, many of them subconscious. What's more, subtle and not-so-subtle cues from our surroundings often "trap" us into eating 100–200 calories more a day than we need or want. The result: Slow but sure weight gain as we age. Here are 7 practical strategies to help you limit those extra calories.

Food psychologist study why we eat the way we do -- and why so many of us are overweight. What these experts are learning is that environmental cues are crucial to overeating. These cues range from package and portion size to plate shape and circumference, the lighting in a room, the presence or absence of others, and the variety of foods offered.

Decreasing your intake by 200 calories a day can add up to a 20-lb weight loss in a year, without having to go hungry or feel irritable. An easy way to do it: Reduce your servings by 20% or leave four or five bites on your plate at every meal. You can also try these strategies:

1. Track the calories you eat -- not only from foods eaten at mealtime but also impromptu nibbles like that handful of M&Ms or those leftovers you snacked on before bedtime. You'll probably find that you are eating more calories than you think. In fact, research shows that the more overweight you are, the more likely you are to underestimate your calorie intake. One study found that fast-food eaters who ate supersized meals underestimated their calorie content by about 40% on average.
2. Use smaller plates, bowls, and utensils, and serve smaller portions. Barbara Rolls, Ph.D., of Pennsylvania State University has found that the bigger the plate, bag, or container, the more food you eat. In several studies conducted at Dr. Rolls' laboratory, people ate 30–50% more when they were given larger vs. smaller portions. They often didn't notice they were eating more, and they didn't feel any fuller. So think small: Down-size your dishes and serving utensils, take advantage of the new 100-calorie snack packs (or make your own), and when you eat out order the small instead of the medium or large.
3. Limit variety. A spread of diverse foods (such as at a buffet) encourages overeating. For instance, Dr. Rolls conducted a study in which people were offered either one flavor of yogurt or three flavors: When they were given a choice of flavors, they ate an average of 23% more yogurt. So limit your plate to no more than two items at a time. You can refill it if you like, but always stick to the two-food limit.

4. Visualize how much you intend to eat beforehand. To prevent overeating, try to visually plan how much you intend to eat before you start a meal -- for example, a cup of soup, a slice of bread, or 3 oz of meal -- and don’t allow yourself to go over the limit (even if your bowl is still full!).

5. Hide the candy and other snack foods. Research shows that people who see more food eat more food. For instance, in one study secretaries ate eight Hershey's Kisses a day when they had an open candy bowl on their desks but only three when the bowl was kept out of sight and six feet away.
6. Do not get distracted. Never eat while doing something else, like watching TV or reading. You're not paying attention to what you're eating -- and that's an invitation to overeat and consume extra calories.
7. Eat alone whenever possible. Research shows that people eat at least one third more when they eat in the company of others, probably because they're not paying close attention to what they consume, the meal lasts longer (allowing more opportunities to nibble), and they may eat to keep up with what their companions are consuming.