“Losing weight is one of the top resolutions made every year, yet only 20 percent of people achieve successful weight-loss and maintenance,” says Jessica Bartfield, who specializes in nutrition and weight management at Loyola University Health System’s Gottlieb Memorial Hospital.

Despite that fact that two-thirds of Americans say they are on a diet to improve their health, very few are actually decreasing in size. “Dieting is a skill, much like playing a musical instrument, and requires practice and good instruction, “ says Dr. Bartfield. “You’re going to hit some wrong notes and feel frustrated, but eventually you will succeed and it will get easier.”

Top Four Reasons Why Dieters Don’t Lose Weight

Here are the top four reasons why many dieters fail to lose weight.

1. Underestimating Calories Consumed

“Most people (even experts!) underestimate the number of calories they eat per day. Writing down everything that you eat- including drinks and "bites" or "tastes" of food - can help increase self-awareness. Pay attention to serving sizes and use measuring cups and spoons as serving utensils to keep portions reasonable. Food eaten outside of the home tends to be much larger portion sizes and much higher in calories. Try to look up nutrition information of your favorite take-out meal or restaurant and select a healthy meal before picking up the phone or going out to eat.

2. Overstimating Activity and Calories Burned

“Typically you need to cut 500 calories per day to lose 1 lb per week. This is very difficult to achieve through exercise alone, and would require 60 minutes or more of vigorous activity every day. A more attainable goal would be to try to increase activity throughout the day and get a total of 30 minutes of moderate to vigorous exercise most days of the week. Buy a pedometer and track your steps; try to increase to a goal of 10,000 steps per day. But be careful- exercise is not an excuse to eat more!”

3. Poor Timing of Meals

“You need a steady stream of glucose throughout the day to maintain optimal energy and to prevent metabolism from slowing down. Eat breakfast every day within one hour of waking up, then eat a healthy snack or meal every three to four hours. Try not to go longer than 5 hours without eating a healthy snack or meal to keep your metabolism steady.”

4. Inadequate Sleep

“Studies have shown that people who get fewer than six hours of sleep have higher levels of ghrelin, which is a hormone that stimulates appetite, particularly for high- carbohydrate /high- calorie foods. In addition, less sleep raises levels of cortisol, a stress hormone, which can lead to weight gain.”