1. Not doing the math
When it comes to counting calories, there's no eyeballing those mashed potatoes for a rough estimate. A reliable calorie calculator will tell you how many calories you are allowed per day based on age, gender, height and level of physical activity. Learning about portions and investing in a food scale can help you make more accurate measurements of how much you should be eating each day.

2. Looking to fad diets
Celebrities are quick to promote methods they employ to lose weight. Often, these diets involve liquid intake for weeks at a time and are not a practical consideration for a permanent lifestyle change, as they can lead to malnutrition and organ failure. Do they yield short-term results? Sure. Even Gandhi would lose weight drinking sugar water!

3. Setting unrealistic expectations
Because every metabolism is different, two people can eat the same amount of food, yet lose weight at different rates. While setting a goal of losing 20 pounds in one month might be plausible, it might not be possible. As long as you hold steady to your weight-loss program, it's best to avoid the "numbers" game. If you must keep track, it's healthy to judge your weight loss with inches lost or simply how your clothing fits.