
Understanding weight
Is Obesity a Disease?
Understand how biology, health and everyday circumstances affect weight, and why long-term support can matter.
Understand obesity and long-term care →For treatment information alongside these guides, see our weight loss medications overview.
Start with clear, practical information on how treatment works and its possible side effects, then use the calculators to understand your calorie needs and whether you may meet the usual starting criteria.

Understanding weight
Understand how biology, health and everyday circumstances affect weight, and why long-term support can matter.
Understand obesity and long-term care →
Beginner's guide
Learn how GLP-1 weight loss injections work, how treatments differ and what to expect from assessment, results and side effects.
Understand weight loss injections →
Beginner's guide
Understand the most common side effects, what may help and when symptoms need prompt or urgent medical advice.
Understand injection side effects →
Calculator
Estimate a practical daily calorie target using your height, weight, age and activity level.
Use the calorie calculator →
Calculator
Check your BMI and get an initial indication of whether you may meet the usual criteria for prescription treatment.
Use the BMI weight loss calculator →Practical advice to help you understand treatment costs, compare options and make a safe, informed decision.
Clear, clinically responsible coverage of developing weight-loss treatments, research and safety questions.
How Often Should You Weigh Yourself on Mounjaro or Wegovy?