Keep a food diary. Studies show that most people underestimate the amount they eat each day. Write down what you eat, where you eat it, what prompts the eating, how it is prepared and the portion size for four to seven days.

Lean what serving sizes really are. You can’t use restaurant servings as a guide, because many are supersized. Try using measuring cups and spoons until you can accurately estimate amounts.

Don’t eat fewer than 1,200 calories a day. Eating less is bound to make you feel hungry and deprived—which can lead to overeating. It also makes it difficult to get enough nutrients.

Don’t eat fewer than three meals a day. Skipping meals slows your metabolism and may lead to excessive snacking or overeating at the next meal. Include healthy snacks as part of your overall daily calorie intake, to help control between-meal hunger and overeating at mealtimes.

Read nutrition labels. Low fat doesn’t always mean low calorie.

Use a pedometer that measures the number of steps you take. Build up to 10, 000 steps a day—about 4 miles depending on your stride. People generally overestimate the amount of physical activity they get in a day.

Adjust the frequency, intensity and duration of your exercise. Work on frequency first. Start by splitting physical activities into several short periods—such as 10 minutes three times a day—so that you get in the habit of exercising daily. Next, work on duration and intensity. Try to accumulate 60 minutes of physical activity over the course of each day.