Obesity is on the rise globally, and tackling it has become a major public health challenge. After a 13-year hiatus, the US food and drug administration (FDA) has approved two new diet drugs. A weight-loss pill called Qsymia received market approval last month, shortly after another, Belviq, was cleared by the agency. “They should reach us within six months," says Vikas Ahluwalia, senior consultant, bariatric and metabolism, Max Super Speciality Hospital, Saket, New Delhi.

According to World Health Organization (WHO) statistics, the number of obese adults globally will rise from the present 400 million to 700 million by 2015. India, too, is witnessing a rise in the number of overweight people, especially in metropolitan centres: Between 12% and 14% of adults are obese, according to the NFHS-3 (National Family Health Survey) and FHS (Family Health Survey), 2011, data. “Obesity has vast economic and health consequences, and aggressive measures for awareness and control should be initiated immediately," says Anoop Misra, chairman, Fortis C-DOC Centre of Excellence for Diabetes, Metabolic Diseases and Endocrinology, New Delhi.

But doctors warn against the indiscriminate and unsupervised use of diet pills, generally recommending regular exercise and a change in diet.

Slimming pills: Doctors emphasize that no drug can cure obesity.

Most diet drugs, including the latest pills, suppress appetite. Belviq controls the appetite by activating the brain receptors for a neurotransmitter called serotonin, which triggers feelings of satiety and satisfaction. This is more sophisticated in its action than weight-loss drugs such as amphetamines, the most popular diet drugs in the 1950s. These worked by raising energy levels, suppressing the appetite and pushing the body to burn more calories. Consequently, they sent the body into overdrive, leading to heart problems, chest pain, palpitation and insomnia. “Pills that suppress your appetite or help you burn your food faster are both unhealthy and ineffective when it comes to maintaining long-term weight loss," says Shipra Saklani Mishra, clinical nutritionist, Fortis La Femme, New Delhi.

While amphetamines were banned many years ago, people still buy them online, and often land up in hospitals after large doses. “Too many diet pills with amphetamines can lead to seizures, severe headaches, blurred vision and vomiting," says Sujeet Jha, director, diabetes and endocrinology, Max Healthcare, New Delhi.

Yet the market for slimming drugs is booming. Decision Resources, a pharmaceutical advisory firm, estimates that the market for obesity drugs will grow fivefold from $478 million (around 2,648.59 crore) in 2006 to $2.7 billion by 2016. Regulations for such drugs are stringent in the US and UK, but a range of diet pills and powders sit on Indian market shelves. Doctors here say these are avoidable and should not be consumed by just anyone. Only those who are obese and suffering from conditions related to this should take prescribed ones, which doctors term “lifestyle medications" rather than “diet pills".

“We prescribe these only to those people with a BMI (body-mass index) over 27, as part of a broader weight-loss regime that involves other medications such as diuretics and a calorie-restricted diet and exercise," explains Dr Ahluwalia.

Creating a pill that fights fat is no easy task and diet pills have historically made bad news for their adverse health consequences. Most weight-loss drugs can affect heart health in the long run, so drug developers have a high safety bar to clear. The last weight-loss medication to gain clearance in the US was Orlistat, in 1999, and today this is the only over-the-counter drug approved for long-term weight loss in the US; it is recommended by obesity experts in India too. “I prescribe Orlistat to two-three patients a day with a BMI over 27, who have some other weight-related condition such as diabetes or high blood pressure," says Dr Jha. He stresses that this pill is not for everyone. Also, it only helps a user lose 2-3kg a year, insignificant for those struggling with the complications of obesity.

Orlistat prevents fat absorption in the body by inhibiting the gastric enzymes that help digest dietary fat. Research so far shows that though this has no life-threatening side effects, the gastrointestinal complications of these pills make it difficult for users to stick to their regime. “In the beginning, diarrhoea and oily stools bother people, though these tummy problems may reduce over time. But this affects compliance and many stop the pill as a consequence," explains Dr Jha. Orlistat should not be taken by anyone who suffers from malabsorption and nutritional deficiencies. “Orlistat is also avoidable for those who are anaemic or have vitamin B12 deficiency," cautions Dr Ahluwalia. Also, this drug has some uncomfortable side effects. “It prevents fat absorption from the food, and may lead to deficiencies. Since fat-soluble vitamins aren’t absorbed, a user may suffer diarrhoea too," says M.P. Sharma, internal medicine specialist, Rockland Hospital, Delhi. He stresses that Orlistat (known as Xenical in India) should be taken under medical supervision.

Another obesity pill, Sibutramine, came into the market in 1997, and doctors say this was quite popular. Though this was FDA-approved and widely prescribed in India, it was banned in 2010 owing to health-damaging side effects. “This led to high blood pressure and heart problems for some," says Dr Ahluwalia.

The new obesity medications too come with their own side effects. Qysmia and Belviq are prescription drugs, since they carry the risk of adverse health issues: Qysmia can increase the heart rate and will not be recommended for patients with heart disease while Belviq is associated with migraines and depression. Only time will prove whether their efficacy will override health concerns.

Ultimately, “no weight-loss medication can remedy a lifestyle problem. In the end, you will stay fat unless you make the changes you need to in your life," says Dr Ahluwalia.

The final verdict? Good eating habits and regular exercise remain the only healthy and effective way of losing that flab.

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