Worked examples: what really happens
Here is the same 80 pound goal for two people, each eating 500 calories a day less than they burn at the start, a plan that would take 80 weeks by the 3,500 calorie rule.
How long does it take to lose 80 pounds?
A quick answer, a calculator for your own timeline, and worked examples showing why 80 pounds often takes a bit longer than the simple math suggests.
At a steady 1 pound a week, losing 80 pounds takes about 80 weeks (roughly 18.5 months). In practice it usually takes a little longer, because weight loss slows as you get lighter. In our worked examples it took about 85 to 86 weeks.
Get your own 80 pound timeline
Timeline Facts
Your projected weight loss
Goal date
Time to goal
Weight to lose
Daily caloriescal/day
To start
Near your goal
To maintain at goal
Starting pace per week
First 5% lost in
First 10% lost in
Day-by-day estimate using the Mifflin-St Jeor equation, re-estimated as your weight changes. Real progress varies week to week; this is not medical advice.
Projected weight by week
| Pace | Time |
|---|---|
| Gentle: 0.5 lb a week | 160 weeks (about 37 months) |
| Steady: 1 lb a week | 80 weeks (about 18.5 months) |
| Fast: 1.5 lb a week | 53 weeks (about 12.5 months) |
| Very fast: 2 lb a week | 40 weeks (about 9 months) |
Simple arithmetic: 80 pounds divided by the weekly pace. Real progress is usually a little slower; see the worked examples below.
| Example | 3,500 calorie rule | Recalculating every 10 lb | Never adjusting calories |
|---|---|---|---|
| A 35-year-old woman, 225 to 145 lb | 80 weeks (about 18.5 months) | 86 weeks (about 19.5 months) | More than 3 years |
| A 35-year-old man, 250 to 170 lb | 80 weeks (about 18.5 months) | 85 weeks (about 19.5 months) | More than 3 years |
Examples: a 35-year-old woman, 5 ft 5 in, lightly active; a 35-year-old man, 5 ft 10 in, lightly active. Modeled day by day with the Mifflin-St Jeor equation.
Look at the last column. Someone who works out their calories once at the start and never adjusts them slows to a crawl before losing all 80 pounds, because by then those calories nearly match what their smaller body burns. This is a common reason bigger goals stall, and recalculating every 10 pounds avoids it.
Planning for a big goal
A 80 pound goal is a long project, often a year or more. It helps to break it into stages of 10 to 20 pounds, recalculate your calories at each stage, and plan short maintenance breaks if you feel worn down. With this much to lose, it is worth involving your doctor, who can check medications that may need adjusting as your weight drops and discuss whether other treatment options could help.
How to make 80 pounds stick
- Aim for a pace you could keep for twice as long as you plan to. Consistency beats a fast start.
- Keep protein high and do some strength training to hold on to muscle while you lose fat.
- Weigh yourself a few times a week and watch the average, not single days.
- Work out your maintenance calories at your goal weight before you get there. The calculator above shows it.
Questions people ask
How long does it take to lose 80 pounds?
At a steady 1 pound a week, losing 80 pounds takes about 80 weeks (roughly 18.5 months). In practice it usually takes a little longer, because weight loss slows as you get lighter. In our worked examples it took about 85 to 86 weeks.
Can I lose 80 pounds in a month?
Not safely for most people. 80 pounds in a month would mean losing about 18 pounds a week, well beyond the 1 to 2 pounds a week the CDC describes as gradual and steady. Plan on at least 40 weeks, and more likely 80 or longer.
How many calories should I eat to lose 80 pounds?
About 500 calories a day less than you burn is a common starting point for losing roughly a pound a week. Use the calculator above or our TDEE calculator to find your number, and recalculate every 10 pounds.
How much will I weigh after losing 80 pounds?
That depends on where you start. Enter your current weight above and the calculator fills in your goal and shows a week-by-week projection.
Sources
- Mifflin MD, St Jeor ST, Hill LA, et al. A new predictive equation for resting energy expenditure in healthy individuals. American Journal of Clinical Nutrition. 1990;51(2):241–247.
- Hall KD, Sacks G, Chandramohan D, et al. Quantification of the effect of energy imbalance on bodyweight. The Lancet. 2011;378(9793):826–837.
- Thomas DM, Martin CK, Lettieri S, et al. Can a weight loss of one pound a week be achieved with a 3500-kcal deficit? Commentary on a commonly accepted rule. International Journal of Obesity. 2013;37(12):1611–1613.
- Centers for Disease Control and Prevention. Losing Weight.