dranupdhir@hotmail.com 
Most people still think of obesity drugs as a shortcut. A pill you take instead of eating less and moving more. That framing has stuck around for a long time, and it's wrong in a specific medical sense.
Obesity is a chronic disease. It changes how the brain signals hunger, how the gut responds to food, and how fat is stored at a hormonal level. Telling someone with obesity to simply eat less is about as clinically useful as telling someone with hypertension to relax. The underlying physiology is working against them, and these medications are what actually target that physiology.
The last five years have changed this field more than the previous two decades. A class of drugs called GLP-1 receptor agonists has produced weight loss outcomes that older medications couldn't come close to, and the cardio metabolic data from trials like SELECT has forced a genuine reassessment of what these drugs are actually for.
What follows is an honest account of how they work, what they do beyond moving the scale, and what their real limits are.
These medications don't all work the same way. Grouping them together as "obesity drugs" obscures some important clinical distinctions.
GLP-1 and Dual Agonists: Semaglutide and Tirzepatide
GLP-1 (glucagon-like peptide-1) is a hormone the gut produces naturally after eating. It slows stomach emptying, sends fullness signals to the brain, and triggers insulin release in response to food. Semaglutide mimics this hormone in a long-acting injectable form. Tirzepatide targets both GLP-1 and GIP receptors simultaneously, which produces stronger effects on appetite and glucose metabolism.
Clinical trials for semaglutide (Wegovy) showed average weight loss of around 15% of body weight. Tirzepatide (Mounjaro/Zepbound) reached approximately 20-22% in some trials. These numbers weren't achievable with older drugs, and they came with meaningful improvements in blood sugar, blood pressure, and cardiovascular risk.
Sympathomimetic Stimulants: Phentermine
Phentermine is older and takes a different route. It stimulates the central nervous system to suppress appetite and slightly raises resting energy expenditure. It's designed for short-term use, typically no longer than 12 weeks, because it raises heart rate and blood pressure, which becomes a clinical problem in patients with cardiovascular conditions. Patient selection matters considerably here.
Lipase Inhibitors: Orlistat
Orlistat works in the gut rather than the brain. It blocks the enzyme that breaks down dietary fat, so roughly 30% of consumed fat passes through undigested. It's available at a lower dose over the counter (Alli) and at a higher prescription dose (Xenical). Weight loss results are more modest than GLP-1 agents. The limiting factor is tolerability; the gastrointestinal side effects are unpleasant enough that many patients stop taking it.
Combination Agents: Naltrexone-Bupropion (Contrave)
This combination works on two pathways at once. Bupropion acts on the hypothalamus to reduce appetite. Naltrexone targets the brain's reward pathway, reducing the reinforcing pull of food. The combination works better than either drug used alone.
Blood Sugar and Metabolic Control. GLP-1 agents were originally developed for type 2 diabetes. They lower blood glucose through insulin stimulation and glucagon suppression. Some patients with early type 2 diabetes reach remission on these medications.
Liver. There's growing evidence that GLP-1 drugs reduce inflammation in metabolic dysfunction-associated steatotic liver disease (MASLD), which affects a significant proportion of people with obesity.
Joints and Sleep. Weight loss of 10-15% of body weight produces measurable reductions in joint load in osteoarthritis. Obstructive sleep apnea severity improves with significant weight reduction. These are outcomes documented in clinical trials, not incidental observations.
A prescription isn't based on BMI alone. A doctor considering anti-obesity pharmacotherapy looks at the whole picture.
Current guidelines generally support medication when BMI is 30 or above, or from 27 upward when weight-related conditions like type 2 diabetes, hypertension, or sleep apnea are already present. Those numbers are a starting point, not a decision.
The underlying conditions shape drug choice substantially. A patient with type 2 diabetes and cardiovascular disease is a different clinical case from someone with obesity and no other metabolic problems, and the preferred agents differ accordingly. Drug interactions and contraindications get checked against the patient's existing medications. Side effect tolerability has to be realistic for that individual. And these medications are meant to work alongside dietary changes and physical activity, because the data consistently shows better outcomes when both are present.
Weight tends to return when medication stops. That's the biology of a chronic disease, not a character failing. For many patients this becomes a long-term commitment, and that needs to be part of the conversation before starting.
Anti-obesity medications have genuinely improved. GLP-1 agents produce weight loss and cardio metabolic outcomes that older drugs didn't. They also carry real side effects, real contraindications, and real costs.
They're tools. They work best as part of a monitored treatment plan that includes dietary support and honest long-term expectations. Using them without medical oversight, which has become easier as online prescribing has expanded, carries risks that don't show up in the marketing.
Considering anti-obesity medication as part of a weight management plan? Consult Dr. Anup Dhir at Image Medical Center, Nehru Place, New Delhi.
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