BMI FAQ : Common Questions About Body Mass Index

This BMI FAQ answers the most common questions about calculating and interpreting Body Mass Index. Whether you're looking to know how to calculate BMI, what is ideal BMI, or if BMI is reliable, you'll find answers here.

BMI is a simple but useful tool to assess your body mass. However, it has its limits and should be complemented by other indicators. Don't hesitate to consult a healthcare professional for a complete assessment.

In the United Kingdom, the NHS provides structured weight management services organised into tiers. Tier 2 services include community-based lifestyle and weight management programmes, typically 12-week group sessions covering diet, physical activity, and behavioural change, available through GP referral at no cost. Tier 3 services are specialist multidisciplinary clinics offering intensive support, including dietitians, psychologists, and physician-led care for individuals with a BMI of 35+ (or 30+ with comorbidities). Tier 4 is bariatric surgery, available on the NHS for patients with a BMI of 40+ or 35+ with serious obesity-related conditions, following assessment through a Tier 3 programme. Waiting times for Tier 3 and 4 services vary by region but can exceed two years in some NHS trusts.

In the United States, the Affordable Care Act (ACA) requires most health insurance plans to cover obesity screening and counselling as a preventive service with no out-of-pocket cost to the patient. The US Preventive Services Task Force (USPSTF) gives a "B" recommendation for screening all adults for obesity, meaning insurers must cover it. Medicare specifically covers up to 22 intensive behavioural therapy (IBT) sessions per year for beneficiaries with a BMI of 30 or higher. Coverage for anti-obesity medications such as semaglutide (Wegovy) and tirzepatide (Zepbound) varies significantly between plans, with many private insurers now adding coverage following FDA approvals while Medicare Part D currently excludes weight-loss drugs under most circumstances.

In Australia, the Medicare system covers GP visits including weight assessments at no out-of-pocket cost with a bulk-billed appointment. The Chronic Disease Management plan (formerly known as EPC, Enhanced Primary Care) allows GPs to refer patients with a BMI above 30 to up to 5 allied health sessions per year, including consultations with dietitians and exercise physiologists, subsidised through Medicare. Private health insurance extras policies often cover additional dietitian consultations and gym memberships. The CSIRO Total Wellbeing Diet program, developed by Australia's national science agency, is one of the country's most recognised evidence-based weight management programmes and is available online nationwide.

Globally, BMI thresholds are being reconsidered by medical authorities. In June 2023, the American Medical Association (AMA) adopted a landmark policy recognising BMI's limitations as a sole diagnostic measure. The AMA now recommends that BMI be used in conjunction with other metrics including waist circumference, body composition (via DEXA or bioelectrical impedance), metabolic markers (blood glucose, cholesterol, blood pressure), and genetic or ethnic factors. This shift acknowledges that BMI alone can misclassify metabolically healthy individuals as unhealthy and vice versa. The policy encourages clinicians to move toward a more holistic assessment of weight-related health rather than relying on a single number derived from height and weight.