Most health authorities agree that losing 1 to 2 pounds (0.5 to 1 kilogram) per week is the safest and most sustainable rate for weight loss. This gradual approach minimizes health risks while maximizing long-term success, as rapid weight loss often leads to muscle loss, nutritional deficiencies, and weight regain. The recommendation is consistent across medical institutions like the Mayo Clinic, Johns Hopkins Medicine, and the NHS, which emphasize lifestyle changes over quick fixes. For context, achieving this requires a daily calorie deficit of 500 to 750 calories, typically through a combination of diet and exercise.

Key findings from the sources include:

• Losing more than 2 pounds per week is considered unsafe for most people, risking muscle loss, bone density reduction, and gallstones ^[3].
• A 0.4–0.6% loss of total body weight per week is the recommended range for most adults, with a broader acceptable range of 0.3–0.9% ^[5].
• Sustainable weight loss relies on long-term habits, including portion control, regular physical activity, and behavioral strategies ^[2].
• Rapid weight loss diets (e.g., very low-calorie diets under 800 calories/day) should only be attempted under medical supervision ^[3].

Safe and Sustainable Weight Loss Guidelines

Recommended Weekly Weight Loss Rates

Medical experts universally advocate for a gradual weight loss of 1 to 2 pounds (0.5 to 1 kg) per week as the safest and most effective approach. This rate is supported by multiple institutions, including the Mayo Clinic, which notes that it requires burning 500 to 750 calories more than consumed daily ^[1]. The NIH further specifies that reducing daily calorie intake by 500 calories typically results in a 1-pound weekly loss, aligning with this guideline ^[9].

The Reddit discussion on safe weight loss rates introduces a percentage-based approach, suggesting a 0.4–0.6% loss of total body weight per week as the standard recommended range, with an acceptable broader range of 0.3–0.9% ^[5]. For example:

• A 200-pound (91 kg) individual could safely aim for 0.8 to 1.2 pounds (0.36 to 0.54 kg) per week (0.4% of body weight).
• The upper limit of 0.9% would allow up to 1.8 pounds (0.82 kg) weekly for the same person, though this may approach the cautionary threshold for rapid loss.

Why this rate is recommended:

• Preserves muscle mass: Losing weight too quickly often results in muscle loss rather than fat loss, which can weaken metabolism ^[3].
• Reduces health risks: Rapid weight loss is linked to gallstones, nutritional deficiencies, and bone density loss ^[3][6].
• Supports long-term maintenance: Gradual loss is associated with better sustained results, as it allows time to adopt permanent lifestyle changes ^[4].

Exceptions and considerations:

• Medically supervised rapid weight loss (e.g., very low-calorie diets of 800 calories/day) may be prescribed for individuals with obesity, but only for up to 12 weeks and under strict monitoring ^[3].
• Initial weight loss phases (e.g., the Mayo Clinic Diet’s "Lose It!" phase) may result in 6 to 10 pounds (2.7 to 4.5 kg) lost in two weeks, but this is designed as a short-term jumpstart followed by a slower, sustainable phase ^[8].

Risks of Rapid Weight Loss and Who Should Avoid It

Losing more than 2 pounds (1 kg) per week is widely discouraged due to significant health risks. MedlinePlus explicitly warns that rapid weight loss can lead to:

• Muscle loss, which reduces metabolic rate and makes weight maintenance harder ^[3].
• Loss of bone density, increasing fracture risk, particularly in older adults ^[3].
• Gallstones, a common complication when losing weight too quickly ^[3].
• Nutritional deficiencies, as restrictive diets often lack essential vitamins and minerals ^[6].

Populations at higher risk:

• Children, teens, and pregnant women should avoid rapid weight loss unless medically supervised, as it can harm development and fetal health ^[3].
• Older adults are more vulnerable to muscle and bone loss, making gradual weight loss critical ^[3].
• Individuals with chronic conditions (e.g., diabetes, heart disease) should consult a healthcare provider before starting any weight loss plan ^[6][10].

Psychological and behavioral risks:

• Rapid weight loss often leads to yo-yo dieting, where lost weight is regained quickly, sometimes with additional gain ^[4].
• Restrictive diets can trigger disordered eating patterns and increase stress, undermining long-term success ^[7].

*When rapid weight loss might be considered:*

• For individuals with severe obesity (BMI ≥ 40), medically supervised very low-calorie diets (VLCDs) may be used short-term to reduce health risks like diabetes or hypertension ^[3].
• Pre-surgical requirements (e.g., before bariatric surgery) sometimes necessitate rapid loss under medical guidance ^[3].
• Even in these cases, the maximum recommended duration is 12 weeks, followed by a transition to a sustainable plan ^[3].