Weight Loss Statistics: Real-World Outcomes by the Numbers

About 20% of people with overweight succeed at long-term weight loss, defined as losing at least 10% of body weight and keeping it off for at least a year

Review drawing on the National Weight Control Registry. After 2-5 years of successful maintenance, the chance of longer-term success rises sharply.

National Weight Control Registry members lost an average of 33 kg and kept it off for more than 5 years

They report about an hour a day of physical activity, a low-calorie and low-fat diet, regular breakfast, self-weighing and a consistent eating pattern. Registry members are a self-selected group of successes.

The 3,500-kcal-per-pound rule grossly overestimates actual weight loss when checked against seven supervised weight-loss experiments

A fixed daily deficit does not keep producing the same weekly loss; the authors provide a validated dynamic model instead.

Exercise programmes produce less weight loss than predicted mainly because the prescribed exercise burns few calories and people eat more alongside it

Systematic review of exercise trials that monitored compliance and measured body composition, tested against energy-balance calculations.

Keeping body weight 10% or more below its starting level reduced daily energy expenditure by 6-8 kcal per kg of fat-free mass

18 obese and 23 never-obese adults. For 60 kg of fat-free mass that is 360-480 kcal a day (our arithmetic).

Obese patients who said diets did not work for them underreported their food intake by 47% and overreported their physical activity by 51%

Measured in 10 'diet-resistant' patients from 224 consecutive obese patients; their energy expenditure was within 5% of predicted.

All 22 reviewed studies of self-monitoring diet, exercise or weight found it consistently associated with weight loss, though the evidence was weak

Systematic review of studies from 1993-2009; samples were mostly white women, and adherence was usually self-reported.

Daily weighers lost 6.1 kg more over 6 months than participants who weighed less than daily

47 overweight adults in the intervention arm of a trial; those weighing less than daily still did so 5.4 days a week.

81% of diet-only groups and 39% of diet-plus-exercise groups lost at least 15% of their weight loss as fat-free mass

Systematic review of 52 studies in adults aged 50 and over with a BMI above 25; the exercise was mainly aerobic.

In lean, resistance-trained athletes in a calorie deficit, fat-free mass fell 0.3-2.7 kg in nine of 13 study groups; the review recommends 2.3-3.1 g of protein per kg of fat-free mass

Systematic review of six studies. The group in a substantial deficit that kept its lean mass ate the most protein, 2.5-2.6 g/kg.

A lifestyle programme aiming for at least 7% weight loss and 150 minutes of activity a week cut diabetes incidence by 58%; metformin cut it by 31%

3,234 adults with raised blood glucose, followed for an average of 2.8 years. Incidence was 11.0, 7.8 and 4.8 cases per 100 person-years with placebo, metformin and lifestyle.

Treating 6.9 people with the lifestyle programme for three years prevented one case of diabetes, against 13.9 people on metformin

Same trial; the lifestyle intervention was significantly more effective than the drug.

Twelve years after gastric bypass, patients still weighed 26.9% less than at baseline (35.0 kg), against 2.0% for patients who sought but did not have surgery

1,156 people with severe obesity, over 90% followed up. Diabetes was in remission in 51% of surgical patients who had it at baseline.

Weekly semaglutide 2.4 mg produced a 14.9% mean weight loss over 68 weeks, against 2.4% with placebo

1,961 adults without diabetes, both groups with lifestyle support. 86.4% on semaglutide lost at least 5% and 50.5% at least 15%.

Partial sleep deprivation increased energy intake by 385 kcal a day without changing energy expenditure

Meta-analysis of 11 studies with 172 participants.

Pedometer indices classify under 5,000 steps a day as sedentary, 7,500-9,999 as somewhat active and 10,000 or more as active

The 10,000-step figure traces to Japanese walking clubs and a business slogan; 5,000-7,499 is 'low active' and more than 12,500 'highly active'.