Doctor explains: Why obesity injections aren’t a ‘quick fix’ for weight loss

Obesity is no longer just a matter of lifestyle but a complex interplay of hormones, genetics, medications, stress, and sleep patterns. In India, rising rates of severe obesity (BMI ≥35) and metabolic obesity, even among those with relatively normal BMI are becoming a growing public health concern. Polycystic Ovary Syndrome (PCOS), thyroid disorders and certain medications are key contributors to weight gain in women, while stress, poor sleep and an “obesogenic” environment further exacerbate the problem.

Newer obesity medications, including semaglutide and tirzepatide, have shown remarkable effectiveness in clinical trials by targeting appetite regulation in the brain, delaying gastric emptying and improving metabolic parameters such as blood glucose, liver fat and cardiovascular risk markers. Yet experts emphasise that weight management requires a holistic approach, addressing hormonal, psychological and lifestyle factors rather than relying solely on pharmacological interventions.

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Firstpost talked to Dr. Subramanian Kannan, Director - Endocrinology and Diabetology at Narayana Health City (Bengaluru) to understand how clinicians determine candidates for obesity injections, the physiological mechanisms of these drugs and the broader strategies needed to tackle the obesity epidemic in India.

How do you determine if a patient is suitable for prescription obesity injections and how soon can they expect significant weight loss?

Dr Kannan: In women, it is found that PCOS or Polycystic Ovary Syndrome is one of the most common causes of obesity and weight gain. And this is predominantly because of the hormonal changes that are happening in the body. So, if we see a young girl who is gaining weight and has irregular periods, we should always screen for PCOS as well.

The other very common cause of obesity is the use of certain medications. For example, steroids, some antidepressants, or even some medications used for diabetes can cause weight gain. So, it is very important to take a detailed history of the patient to understand if any of these medications are the cause of obesity. Obesity Injections can be prescribed in such cases and Weight loss often begins within the first 2 to 4 weeks.

What is the mechanism by which these drugs reduce appetite and body weight in patients?

Dr Kannan: These therapies work by correcting the broken signalling between the gut and the brain. To understand how they work, we must look at the factors they counteract: Poor sleep spikes ghrelin (the hunger hormone) and suppress leptin (the satiety hormone), leading to intense cravings for high-calorie reward foods.

Also, Chronic stress triggers cortisol release, which is directly linked to the accumulation of visceral (abdominal) fat and emotional eating.

So, modern injections simultaneously decrease the neurological drive to eat via brain signalling, increase the physical sensation of fullness by slowing gastric emptying, and enhance overall metabolic efficiency.

Are metabolic complications (type 2 diabetes, NAFLD, hypertension) increasing proportionately with obesity prevalence in recent datasets?

Dr Kannan:  There is a notable concern that patients whose BMI may not be very high (below 25) can still carry a significant burden of metabolic obesity due to visceral adiposity (fat around the internal organs). Obesity is not just about how much you weigh. It's about where the fat is distributed. Central obesity, or fat around the abdomen, is much more dangerous than fat distributed in other parts of the body because it is closely linked to metabolic diseases like diabetes and heart disease. While global data suggests severe obesity numbers may be coming down in some areas, in India, the population with a BMI over 35 or 40 is increasing, which typically correlates with a rise in these metabolic complications.

How does thyroid function influence the development, severity and management of obesity in patients?

Dr Kannan: Thyroid disorders, especially hypothyroidism where the thyroid gland is underactive can also lead to weight gain. This is because the thyroid hormone is responsible for the metabolism of the body. When the levels are low, the metabolism slows down, leading to weight gain even with a normal diet."

How have obesity trends changed in children and adolescents (5–19 years) based on recent multinational surveillance data?

Dr Kannan: Genetics also play a significant role. If both parents are obese, there's an 80% chance that the children will also be obese. However, genetics only provide the predisposition; the environment and lifestyle choices act as the triggers. So, even with a genetic tendency, a healthy lifestyle can help prevent obesity.

What is your perspective on public perception vs. clinical reality regarding “quick fixes” in obesity treatment?

Dr Kannan: Environmental factors are also very important. The availability of cheap, high-calorie processed foods and the sedentary nature of our modern jobs have created what we call an 'obesogenic environment.' It has become very easy to consume calories and very difficult to burn them off."

Lastly, we must talk about the psychological impact. Obesity is often associated with depression, low self-esteem, and social isolation. It’s a vicious cycle where the psychological state leads to weight gain, and the weight gain further worsens the psychological state. Treatment should always be holistic, addressing both physical and mental health.

Are we seeing a faster rise in severe obesity (BMI ≥35 or ≥40) compared to moderate obesity globally?

Dr Kannan: Worldwide, does indicate that there's a lesser amount of people with severe obesity. So the data indicates globally that the number of people with severe obesity is coming down. However, in India, it is a concern that this group of the population, with a BMI of more than 35 or more than 40, is starting to increase. Also, what worries us is that there's also a problem where patients whose BMI may not be very high, maybe below 25, but still carry the burden of metabolic obesity because of visceral adiposity as well. So, while the global severe obesity may be coming down, in India, we are seeing patients with higher BMIs, greater than 35 and greater than 40.

Can you explain how the newer obesity medications work at a physiological level?

Dr Kannan: Newer obesity medications, such as semaglutide (a GLP-1 receptor agonist) and tirzepatide (a dual GIP/GLP-1 receptor agonist), manage weight by mimicking natural "incretin" hormones produced in the gut. They act on three primary physiological systems: the brain, the digestive tract, and the metabolic tissues.

How effective are semaglutide and tirzepatide in terms of mean percentage body weight reduction in clinical trials?

Dr Kannan: At a physiological level, these medications bind to and activate GLP-1 receptors located in several key organs:

Brain: They act directly on the brain’s hunger and satiety centers to increase feelings of fullness and significantly reduce "food noise" (intrusive thoughts about eating). This suppresses appetite and reduces overall caloric intake.

Digestive Tract: They delay gastric emptying, meaning food stays in the stomach longer. This physical delay creates a prolonged sensation of fullness after meals.

Pancreas: They stimulate insulin secretion and suppress glucagon release in a glucose-dependent manner, which stabilizes blood sugar and prevents the metabolic crashes that often trigger cravings.

How do these drugs impact metabolic parameters such as blood glucose, lipids, blood pressure and NAFLD markers?

Dr Kannan: These medications are highly effective at reducing liver fat and inflammation. Clinical markers show a significant decrease in liver enzymes (ALT and AST), and imaging confirms that hepatic fat content can drop by 30% to 50%.

Users typically experience a reduction in both systolic and diastolic blood pressure. While the drugs have some direct vascular effects, much of this improvement occurs because weight loss reduces the workload on the heart.

What does current evidence say about cardiovascular risk reduction (if any) with obesity injections?

Dr Kannan: Current evidence shows that obesity injections—specifically GLP-1 and dual GIP/GLP-1 receptor agonists—provide significant cardiovascular protection. The most robust evidence comes from large-scale cardiovascular outcome trials (CVOTs), which demonstrate that these medications reduce the risk of major adverse cardiovascular events (MACE) like heart attack and stroke.