Safe weight loss rate: how fast to lose, and why the first 5% matters most

The pace health services recommend

Three public health bodies converge on the same order of magnitude.

• The NHS advises aiming to lose 1 to 2 pounds, or 0.5 to 1 kilogram, a week, and warns against losing weight suddenly with diets.
• The CDC says that people who lose weight at a gradual, steady pace of about 1 to 2 pounds a week are more likely to keep the weight off.
• The Haute Autorité de Santé, for adults with obesity, recommends realistic goals of 1 to 2 kilograms a month on average, within a plan agreed with the doctor.

The ranges are wide on purpose. Someone with a lot of weight to lose usually loses faster at the start than someone close to their goal, for the same effort.

The goal that already changes your health

Many people set a target weight from a chart or from memory of their twenties. The guidelines take a different view. The 2013 guideline of the American Heart Association, the American College of Cardiology and The Obesity Society says that a modest, sustained loss of 3 to 5% produces clinically meaningful benefits, and that greater losses bring greater benefits. The Haute Autorité de Santé adds that a loss of 5 to 10% reduces the risk of developing type 2 diabetes.

For an illustrative person of 82 kilograms, 5% is about 4 kilograms. At half a kilogram a week, that is a matter of two months, not a year. It is a first goal you can reach, measure and celebrate before deciding on the next.

Your waist tells part of the story the scale misses; see waist-to-height ratio.

Is fast weight loss regained faster?

The usual explanation for preferring a slow pace is that weight lost quickly comes back quickly. The best trial on the question does not support that claim. Purcell and colleagues randomised 200 adults with obesity to a 12-week rapid programme or a 36-week gradual one, both aiming at 15%. After almost three years, both groups had regained most of what they had lost, about 71% in each, with no difference due to the speed of loss.

The same trial carries two other lessons. More participants reached the target in the rapid group, 81% against 50%. And one person in the rapid group developed gallbladder inflammation requiring surgery. Rapid loss was done here within a hospital-based programme.

So the pace does not decide whether you keep the weight off; what you do afterwards does. The reasons to prefer a moderate pace on your own are safety, energy for work and training, and a plan you can live with. Keeping the weight off is covered in keeping weight off.

How to set your pace with the calculator

The calculator on this page turns your goal into a number of weeks at the pace you choose, and checks that pace against the NHS range. Take an illustrative woman of 52, 82 kilograms and 163 centimetres, with a desk job and no structured exercise: the Mifflin-St Jeor equation gives about 1,420 kilocalories at rest and about 1,700 for the day.

The 2013 guideline lists a deficit of 500 or 750 kilocalories a day, or an intake of about 1,200 to 1,500 kilocalories for women and 1,500 to 1,800 for men, adjusted to body weight. For her, a 500 kilocalorie deficit lands at about 1,200, the lower edge of the range. That is a signal: adding activity, which raises her needs, is a gentler way to widen the gap than eating less still. Calorie deficit details the method, and exercise to lose weight the training side.

When faster is too fast

The 2013 guideline is explicit: a very low calorie diet, defined as fewer than 800 kilocalories a day, should be used only in limited circumstances, by trained practitioners in a medical setting with monitoring. The Haute Autorité de Santé asks doctors to warn against overly restrictive and unbalanced diets, and against repeated diets that cause weight fluctuations, which can be harmful to health.

On your own, a few signals suggest the deficit is too large:

• Your weekly average is falling well beyond 1 kilogram a week for several weeks.
• You are hungry most of the day, sleep badly or feel dizzy.
• Your training is getting worse rather than better, session after session.
• You find yourself thinking about food constantly, or swinging between strict days and lost control.

The answer is not to try harder, but to eat a little more and let the pace slow down.

Protecting muscle along the way

A slower pace makes it easier to lose fat rather than muscle, with two allies. Resistance training, which the ACSM position stand on weight loss found may increase fat-free mass and the loss of fat mass. And enough protein: a meta-analysis by Wycherley and colleagues found better preservation of lean mass with higher-protein diets at the same calorie level. See protein for weight loss.

Talk to your doctor before starting if you are pregnant or breastfeeding, have diabetes, heart, kidney or liver disease, take regular medication, have a history of eating disorders, or have a lot of weight to lose. Unexplained weight loss, without trying, always needs medical advice.

A pace you can keep, with Never Skip Club

Safe weight loss is a matter of months, and months are won one week at a time. Create your free account on Never Skip Club, launch guided sessions adapted to your level, from Easy to Intense, and start a crew with friends who share your rhythm: the ranking rewards the sessions you keep, not the ones you overdo. If you want a professional to set your training around a medical plan, find a coach from our network, or sign in to book.