Why Am I Not Losing Weight in a Calorie Deficit? Dietitians Reveal 6 Common Mistakes and Fixes

If you’re eating less, moving more, and still not seeing the number on the scale go down, you may be wondering: “Why am I not losing weight in a calorie deficit?” Experts say this is more common than you think—and it doesn’t always mean you’re doing something wrong. From hidden tracking mistakes to metabolic changes, here’s what could be holding up your progress. 

How a calorie deficit works for weight loss

A calorie deficit is when you take in fewer calories than your body uses to meet your energy needs (which varies between individuals), explains Palina Lancaster, RDN, Director of Dining Services and dietitian at Morrison Healthcare. Essentially, you’re burning more calories than you’re consuming. As a result, your body uses stored fat to burn energy, which is what contributes to your weight loss progress.

To effectively lose about 1 pound per week, you’d need to reduce your daily caloric intake by about 500 calories per day over seven days, she explains.   

4 common tracking mistakes that can sabotage your calorie deficit

While not a requirement for sustainable weight loss, many people opt to log their daily calorie intake. However, this practice is not a perfect science. Experts say these are the most common errors people make when logging food: 

Eyeballing portions instead of measuring

While it’s tempting to assume you know how much food or drink you’re consuming, it’s very easy to underestimate if you’re eyeballing portions. Using a digital food scale to weigh each ingredient in grams is the best bet for precision, advises Trista Best, RD at Balance One Supplements. 

Skipping ‘small’ items like oils, dressings and bites

Not logging cooking oils, sauces, dressing, butter and other seasonings or ingredients that contain calories is another common misstep. Even if you don’t use large amounts, the calories can add up and can push you over your daily allotment. Best recommends measuring and logging these add-ins separately from your main dish. 

The same goes for grabbing small handfuls of snacks, quick tastes or finishing the last few pieces off of a plate. Liquid calories (especially in denser drinks like alcohol and flavored coffees) also count toward your total. 

Relying solely on food tracking apps

Many food tracking apps will auto-populate suggested calorie counts for certain items. These are often user-generated, so there is quite a bit of room for human error. Also, calories in the same product can vary between different brands. Best suggests double-checking entries with verified sources or food labels, and manually creating custom entries when needed. 

Focusing on calories burned from workouts

It’s usually not recommended to log calories burned during exercise or use these figures to calculate your ideal deficit. That’s because calorie counts on gym equipment like treadmills and even smartwatches can be relatively inaccurate. 

More reasons you’re not losing weight in a calorie deficit 

Calories in, calories out (CICO) is generally considered one of the core components of any weight loss journey. But it’s possible not to lose weight even if you are in a deficit and logging all your food accurately. Here are a few reasons. 

Metabolic adaptation

If you’ve been reducing your calories for an extended period, your metabolism might slow down as your body adjusts to the lower caloric intake, explains Diane Lindsay-Adler, RDN, Assistant Professor of Pediatrics and Adjunct Assistant Professor of Public Health at New York Medical College dietitian at the Armond V. Mascia MD Cystic Fibrosis Center. 

“Weight loss may plateau when your body becomes more efficient at using the calories you consume, making weight loss slow down or stop,” she says. (Learn how to break through a weight-loss plateau here.)

Loss of muscle mass

If you’re not doing strength training or consuming enough protein, you might lose muscle mass as you lose weight, says Lindsay-Adler. Muscle is a more metabolically active tissue than fat, so a decrease in muscle mass can actually slow your metabolism. 

Body recomposition

Sometimes, even though the scale isn’t moving much, your body composition may be changing, notes Lindsay-Adler. You may be gaining muscle while losing fat, so markers like body measurements, the way your clothing fits or progress photos might be more indicative of your weight loss progress than the scale, she offers. 

Health and hormonal factors

A slow thyroid (hypothyroidism) can significantly impact metabolism and make weight loss much harder, even if you’re in a calorie deficit, confirms Lindsay-Adler. Similarly, polycystic ovary syndrome (PCOS) often causes insulin resistance, another weight loss barrier. Additionally, some medications (like some antidepressants, hormones or corticosteroids) can interfere with weight loss, she says. 

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