Why Am I Losing Weight But Not Body Fat?

When looking to get into better shape, many people use weight as a measure of progress. Measurements such as body mass index -- or BMI -- which test your height to weight measurement, aren't an accurate progress gauge, according to Dr. Rexford Ahima, medical professor at the University of Pennsylvania. Measuring your body fat levels is much more accurate, but it can be the case that, while the scales seem to be going down, your body fat isn't dropping.

Close-up of a man's legs standing on a bathroom scale. (Image: Stockbyte/Stockbyte/Getty Images)

You're Dropping Water Weight

It is possible that you're losing water weight, hence the scales are dropping, but you're not making any visible progress in fat loss. This can happen when starting a low-carbohydrate weight loss diet. When eating a higher carb intake, your stores of muscle and liver glycogen are up and this increases the amount of water weight you carry. If you cut carbs, you lose glycogen, which in turn means you drop water and can lose weight very quickly without actually losing any fat.

You're Losing Muscle

Those on very low calorie diets are prone to losing muscle mass. While you probably don't want to look like a bodybuilder, muscle is still important as it helps keep your metabolism ticking over. When your calories drop very low -- usually under 1,200 per day -- you risk losing muscle mass, notes weight loss author Judith J. Wurtman, PhD. Additionally, losing muscle mass when dieting can lead to a larger increase in body fat after going off your diet.

Two Types of Fat

You may be losing fat, but unable to see it. According to the Harvard Medical School, there are two types of fat: visceral and subcutaneous. The subcutaneous fat lies just beneath the skin and is the stuff you can see, whereas visceral fat lies much deeper and surrounds your organs. You may be in the early stages of a weight loss diet and have lost some visceral fat, but not much subcutaneous. This is still beneficial, as higher levels of visceral fat are linked to an increased risk of heart disease and diabetes.

Tools of the Trade

The equipment you're using to test your body fat may not be giving you the full picture. Methods like handheld body fat measures are notoriously inaccurate; even methods such as body fat calliper testing can still be off by quite a bit, notes nutritionist Lyle McDonald. If you're just starting out on a diet, it can be difficult to see any visual progress to begin with. Your best bet is to use a variety of measures, such as weighing yourself, taking progress pictures, recording waist, hip, chest and thigh measurements, and getting a professional body fat test done once every three to six weeks.

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