I lost weight but my body fat percentage barely changed. Why?

Short Answer

When you lose weight on intermittent fasting, some of that weight is fat and some is water, glycogen, and occasionally a small amount of lean tissue. Body fat percentage is a ratio — if you lose both fat and lean mass (or water) at similar rates, the percentage barely moves even as total weight drops. It's a math problem, not a sign the protocol isn't working.

What's Actually Happening

Body fat percentage is calculated as: (fat mass ÷ total body weight) × 100.

This means the percentage can stay flat even while you are genuinely losing fat — if other parts of your body weight are also decreasing at a similar rate.

The glycogen and water effect

When you start intermittent fasting, one of the first things your body burns through is glycogen — the stored form of glucose in your liver and muscles. Glycogen holds water at roughly a 3:1 ratio. As glycogen depletes, you lose several kilograms of water along with it. This is real weight loss on the scale, but it reduces total body weight without reducing body fat.

Example: If you start at 90kg with 30% body fat (27kg of fat), and you lose 3kg of water weight, you're now at 87kg. Your fat is still 27kg. Your body fat percentage has just increased slightly to 31%. In the early weeks, this effect often dominates scale readings.

Measurement error

Consumer body fat scales — the ones built into bathroom scales or fitness trackers — use bioelectrical impedance. They send a weak current through the body and estimate fat based on resistance. These devices are notoriously sensitive to hydration levels, time of day, meal timing, and even temperature. Two readings taken two hours apart on the same person can differ by 3–5 percentage points.

If your body fat readings come from a home scale, the numbers may simply not be accurate enough to detect the changes that are actually happening. DEXA scanning or hydrostatic weighing would give you a more reliable picture.

You may be losing fat and lean mass together

Aggressive fasting without sufficient protein can lead to some loss of lean tissue alongside fat loss. If both fat and lean mass decrease proportionally, body fat percentage barely moves. This is why protein intake matters during fasting — eating adequate protein when you break your fast helps protect muscle mass, which tilts the composition of weight loss more toward fat.

What a good result actually looks like

Losing 1–2% body fat per month while maintaining or gaining lean mass is an excellent outcome. Many people focus too much on the percentage and miss the actual fat mass number. If you've lost 4kg total over six weeks but your body fat percentage dropped only 1%, you may still have lost 2–3kg of actual fat tissue. That's meaningful progress.

What to Do About It

Focus on fat mass, not just the percentage. If your scale gives you weight and a fat estimate, track the absolute fat mass number alongside body weight. A shrinking fat mass number is what you actually want — the percentage is secondary.

Prioritise protein when you break your fast. Eating sufficient protein (roughly 1.6–2.2g per kg of body weight per day for active people) preserves lean mass and shifts the composition of weight loss toward fat.

Add resistance training. Even two sessions per week of bodyweight exercises or weights can meaningfully reduce muscle loss during caloric restriction and fasting. Building muscle while losing fat actually compresses body fat percentage faster.

Give it more time. The glycogen and water phase is temporary — typically the first two to four weeks. Once glycogen stores stabilize at their new lower level, subsequent weight loss is more purely fat. Body fat percentage tracking becomes more meaningful after this initial period.

Get a better measurement. If you're serious about tracking composition, a DEXA scan every three to six months gives you accurate data on fat mass, lean mass, and bone density rather than estimates from a home scale.

Want to Learn More?

Read our full article: Does intermittent fasting burn muscle?

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This article is for informational purposes only and is not medical advice. Always consult a qualified healthcare professional before starting any fasting protocol, especially if you have an existing health condition.