A marijuana joint might seem an odd starting point in the search for weight-loss secrets.
Yet a compound switching off the same brain circuits that make people hungry when they smoke cannabis looks set to become the world's first blockbuster anti-obesity medicine, with sales tipped by analysts to top US$3 billion a year.
Sanofi-Aventis SA's Acomplia, or rimonabant, which could be approved by U.S. regulators as early as next month, is the first of a new wave of treatments that may spell fat profits for some pharmaceutical companies.
Another two experimental drugs from Arena Pharmaceuticals Inc and Alizyme Plc, with different mechanisms of action, have also produced promising clinical results in recent weeks, prompting some investors to start laying big bets on weight-loss medicine.
It is a risky area, however.
Slimming pills have had a chequered history, due to modest effectiveness and adverse side effects - most notoriously with the diet drug combination "fen-phen," which was linked to heart-valve problems and has cost Wyeth more than US$21 billion in provisions related to patient claims.
But past upsets have not deterred drug manufacturers from investing heavily in a new generation of possible winners.
Jonathan de Pass, chief executive of specialist consultancy Evaluate, calculates there are now 26 new drugs in clinical trials for obesity and a further 32 in early-stage development.
In addition, at least half a dozen diabetes medicines are being tried out as treatments for reducing weight.
The potential market is large in every respect.
The World Health organization (WHO) estimates more than 1 billion people in the world are overweight and, if current trends continue, that number will reach 1.5 billion by 2015.
Of the current total, more than 300 million already rank as obese, putting them at substantial risk of heart disease, stroke, type 2 diabetes, respiratory problems and some cancers.
Worryingly, the problem is also starting to spread rapidly in developing countries, including parts of Africa, and the western Pacific islands of Nauru and Tonga hold the dubious distinction of having the highest percentage rates of obesity in the world.
Given the scale of the problem, the arrival of new weight-loss drugs will be greeted with some excitement - but they may also pose a dilemma.
Dr Timothy Armstrong of the WHO's department of chronic diseases believes medication can help only a very small minority of patients and will not impact the overall obesity epidemic.
"It's not a panacea," he said. "Drugs don't have a role in preventing obesity in the wider population, where interventions around physical activity and diet are far more cost-effective."
Professor Luc Van Gaal of Belgium's University Hospital Antwerp, the lead investigator for one of the main clinical studies for Acomplia, sees things rather differently.
He argues doctors must accept that dieting and exercise alone often produce disappointing results, leaving patients at risk of falling seriously ill.
"Drug therapy is not the answer for every obese person in the street, but for certain patients who are running a risk, pharmacological therapy can help," he said.
Today, there are two main obesity medicines on the market - Roche Holding AG's Xenical, which works by limiting fat absorption, and Abbott Laboratories Inc's Meridia/Reductil, which suppresses appetite.
Both can have adverse side effects, however. Xenical can cause excess gas and oily discharge, while Meridia may increase blood pressure. As a result, sales of both drugs are modest, at US$460 million and US$300 million respectively in 2004.
GlaxoSmithKline Plc hopes to win backing from a U.S. panel later this month for its own low-dose, low-side effect version of Xenical that would be sold without prescription - although many industry experts still doubt it will become a major seller.
By contrast, the consensus forecast from analysts for peak sales of Acomplia is US$3.1 billion, according to Evaluate, with some predictions topping US$5 billion.
The company hopes to prove that Acomplia specifically reduces key cardiovascular risk factors, since a simple obesity label may not be enough secure widespread reimbursement from governments and insurers.
Side effects could also be an issue. While patients on Acomplia have lost around 7 kg (15 lb) in body weight over two years, concerns remain about its potential impact on mood.
Still, rivals clearly think Sanofi is onto something big, with Merck & Co Inc, Pfizer Inc and Bristol-Myers Squibb Co among a clutch of companies now developing similar cannabinoid receptor blocking drugs.