Weight gain or obesity
At a visit for weight gain or obesity your doctor will measure your height, weight and waist/neck circumference to calculate your body mass index (BMI). A BMI between 25 and 29.9 indicates overweight and a BMI of 30 or more indicates obesity; class I obesity is 30–34.9, class II is 35–39.9 and class III is 40 or higher. They will ask about your diet, physical activity, sleep patterns, emotional health and family history, review medicines that can cause weight gain and look for signs of hormonal disorders such as thyroid disease or Cushing’s syndrome. Rapid or unexplained weight gain (more than about 10 kg) or symptoms like fatigue, cold intolerance, irregular periods or muscle weakness may prompt blood tests to check your thyroid, cortisol levels and a metabolic panel. Your doctor will discuss your readiness to make changes and work with you to set achievable goals using the 5As approach (Assess, Advise, Agree, Assist, Arrange).
Medicines are used only when lifestyle changes alone aren’t enough and usually require a BMI ≥ 30 or a BMI ≥ 27 with other health problems. Options include a lipase inhibitor (orlistat) that blocks fat absorption, combination medicines such as phentermine–topiramate and naltrexone–bupropion, and injectable or oral GLP‑1 receptor agonists like liraglutide, semaglutide or tirzepatide that reduce appetite and slow digestion. Phentermine by itself is approved only for short‑term use. All weight‑loss medicines can cause side effects and must be prescribed and monitored by a healthcare professional. Treating underlying causes such as hypothyroidism or polycystic ovary syndrome may involve thyroid hormone, hormonal contraceptives or other medications.
In addition to calculating BMI and measuring waist circumference, your provider may order tests to look for medical causes of weight gain and to assess complications. These tests can include:
• A complete metabolic panel (CMP) to check blood sugar, liver and kidney function, and electrolytes; abnormal results can suggest diabetes or organ problems.
• Thyroid‑stimulating hormone (TSH) and free T4 to screen for an underactive thyroid.
• Morning cortisol or late‑night salivary cortisol to evaluate for Cushing’s syndrome if you have central obesity with thin limbs, purple stretch marks, muscle weakness or high blood pressure.
• Fasting glucose and hemoglobin A1c to look for diabetes and insulin resistance.
• Lipid panel to measure LDL, HDL, total cholesterol and triglycerides and assess cardiovascular risk.
• A complete blood count (CBC) to detect anemia or other blood disorders.
Your provider might also order other tests based on your symptoms, such as prolactin, testosterone or estrogen levels, pregnancy test or sleep study if sleep apnea is suspected.
Imaging isn’t usually needed to diagnose weight gain or obesity. Ultrasound or pelvic imaging may be used if conditions such as polycystic ovary syndrome are suspected. Bone density scans (DEXA) are sometimes used to assess body composition or osteoporosis risk. More advanced scans (CT or MRI) are reserved for investigating tumors or rare endocrine disorders.
Seek medical evaluation promptly if you gain weight rapidly (more than 10 kg/22 lb) without changing your diet or activity level, or if weight gain is accompanied by shortness of breath, leg swelling, severe fatigue, weakness, vision changes, easy bruising, purple stretch marks, round face or a hump between your shoulders (possible Cushing’s syndrome). Irregular periods, acne, excess hair growth or infertility may suggest polycystic ovary syndrome. Unintentional weight loss, night sweats or persistent thirst and urination also warrant medical attention.
Follow‑up visits are usually scheduled every 3–6 months to monitor weight, blood pressure, lab results and to adjust the plan. If you start weight‑loss medication, your doctor may see you monthly at first to monitor progress and side effects. Annual visits are important to reassess cardiovascular risk. People who pursue bariatric surgery or have severe obesity may require more frequent visits and coordinated care.
Maintaining a healthy weight is about long‑term habits. Eat a balanced diet rich in vegetables, fruits, whole grains, lean protein and healthy fats while limiting added sugars, salt and saturated fat. Practice portion control, avoid mindless snacking and drink water instead of sugary drinks. Aim for at least 150 minutes per week of moderate‑intensity aerobic activity like brisk walking, cycling or swimming and include muscle‑strengthening activities on two or more days. Manage stress, get adequate sleep and minimise screen time. Keep a food and activity journal or use a smartphone app to track progress. Gradual weight loss (1–2 pounds per week) is safer and more sustainable than crash diets.
Your primary care doctor will coordinate your weight‑management plan. They may refer you to a registered dietitian or nutritionist for personalised meal planning; an endocrinologist if you have a hormonal disorder; a sleep specialist if sleep apnea is suspected; a mental health professional for emotional eating or depression; a physical therapist or exercise physiologist to design a safe exercise program; and an obesity medicine specialist or bariatric surgeon if surgery is an option. Your doctor can also connect you with community weight‑loss programs or support groups.