Nowadays, there are apps and online tools that may provide a better, more realistic assessment of your predicted weight loss.

The Body Weight Planner, developed by the National Institute of Health, provides calorie levels for both weight loss and maintenance.

It takes into account how diet and exercise contribute to weight loss, as well as how your body responds to reduced calorie intake. It has an immense amount of mathematical calculations behind it.

Another good tool to predict weight loss is the Single Subject Weight Change Predictor, developed by the Pennington Biomedical Research Center.

This tool also allows you to calculate weight loss, based on dietary intake and exercise.

The 500-calorie deficit rule is not a realistic way to predict weight loss. Better tools exist to predict weight loss over a period of time.

A pound of body fat may contain anywhere from 3,436 to 3,752 calories.

However, it is a myth that just eating 500 fewer calories per day (3,500 per week) causes weight loss of one pound.

This may work in the short-term, but the body will soon adapt by making you burn fewer calories. For this reason, weight loss slows down over time.