What's actually a safe rate of weight loss?

The 0.5–1 kg per week range (and where it comes from)

The NHS, NIH, CDC and Mayo Clinic converge on the same band: 0.5–1 kg (1–2 lb) per week is safe and sustainable for most adults. It's the rate at which your body can lose fat without disproportionately losing muscle, lowering metabolic rate, or driving the hormonal changes that make regain almost inevitable.

What happens when you go faster — three things, all bad

• You lose more muscle. Muscle is metabolically expensive — lose enough and your daily energy expenditure drops, making the next phase harder.
• Hunger hormones get louder. Sharp deficits drive ghrelin up and leptin down. The discipline that worked last week needs to roughly double next week.
• You learn the wrong habits. Crash protocols teach short-term tricks, not the routines that keep weight off after.

Why slower loss usually means you keep it off

Follow-up data on rapid weight loss is consistent and grim: most of it returns, often plus a little extra, within one to three years. Gradual loss is gentler and more durable.

When faster is OK (medically supervised exceptions)

Pre-surgical weight loss, certain very-low-calorie protocols managed by a doctor, specific clinical situations — these can warrant faster rates. If your doctor told you, follow your doctor. If TikTok told you, please ignore TikTok.

Slower isn't a moral choice. It's the strategy that survives contact with real life.

How to set a pace inside the safe zone

Aim for the middle: 0.6–0.8 kg per week. Treat it as a ceiling, not a target. Slower weeks are normal. Several much-faster weeks in a row? Ease up.

The 2 lb/week cap we built into futureGoal — and why

We cap weight challenges at the upper edge of the safe range and display percentage progress by default. Both choices are deliberate. We'd rather rank lower for "fast weight loss" than nudge anyone past a pace their body can sustain.