Why am I not losing weight in a calorie deficit?

Usually because the deficit is smaller than the math says. Food logs run low, labels run low, and watches guess at the burn. Water on the scale can hide fat loss for a week or two. Before you cut more, weigh in every morning for four weeks and log every bite, oil and drink. The trend shows you which one it is.

You’re probably doing most things right, which is why it’s so frustrating. The gaps are small and easy to miss, and a 500 calorie deficit doesn’t leave much room for them.

The simple version

It’s a bank account where some purchases post late. The balance looks wrong until the whole statement comes in, and the statement here is four weeks of weigh-ins.

Where the gap hides

• The log. In a 2003 US study of 484 adults, people under-reported their calories by 12 to 20% on a careful 24-hour recall, checked against a lab measure of what they burned. On a 2,000 calorie day that’s 240 to 400 calories, most of a 500 calorie deficit.
• The label. US rules let a food hold up to 20% more calories than its label says before it counts as mislabeled. In a 2010 study, 29 restaurant dishes sold as lower-calorie had 18% more calories than stated, on average.
• The watch. If you eat back exercise calories, the watch’s number is a guess: across 56 studies, Apple Watch calories were off by about 28% on average.
• Water. Stored carbohydrate is held with 3 to 4 times its weight in water. So the scale can jump after a pasta night and drop after a low-carb day, fat or no fat.

What to do

• Weigh all your food for three days, oils and drinks included, to see where your log drifts.
• Compare four-week averages, never single days.
• If the trend stays flat with a careful log, your maintenance is lower than you thought. Measure it on the real TDEE calculator and set your target from that.
• If the scale won’t move and you feel unwell, tired or cold, see a doctor.