How big should my calorie deficit be?

Start at about 500 calories a day under your maintenance. It’s the low end of what the US obesity guideline uses (500 to 750), it comes to about a pound a week at first, and it’s small enough to live with. Go toward 750 only if you have a lot to lose. Whatever you pick, the target stays above your floor.

A bigger cut sounds faster, and for a few weeks it looks faster. Much of that early drop is water, because stored carbohydrate is held with 3 to 4 times its weight in water and leaves first. Then the gap shrinks as you get lighter, and the extra speed fades.

The simple version

A deficit is a savings plan run backward. A modest amount every day adds up, and a plan you keep beats a bigger one you quit in March.

Size it to your body

A percent of your weight scales better than one fixed number. Here’s 0.5 to 1% of body weight a week, at 3,500 calories a pound:

Take the lower end if you’re lean or lifting. In a 2011 trial of elite athletes who lifted weights, the group losing 0.7% of their weight a week gained about 2% lean mass, and the group losing 1.4% gained none.

The floor: never under your resting burn, and never under 1,200 calories a day for women or 1,500 for men without a doctor. If the table’s number would take you under it, use a smaller deficit. Under 5,000 steps a day, our calculators put maintenance at 1.2 times resting burn, so the floor leaves room for only about a fifth of your resting burn, around 280 a day for the average American woman. Walking more makes room.

What to do

• Set it on the calories to lose calculator, which finds the pace your floor allows.
• Keep protein in the typical range, 1.2 to 1.6 grams per kilogram of body weight. The protein calculator gives yours.
• Weigh in most mornings and judge by the four-week trend.