Can we control obesity with diet pills and weight loss drugs?

For most of human evolution, we have been fighting a battle against starvation, trying to pack in enough calories to stay alive, now we are facing the opposite problem in the western world with overeating and obesity.  Being overweight or obese poses huge problems for society with increased risk of cardiovascular diseases such as heart attack or stroke as well as increasing the risk of cancer.  It can also cause joint and mobility problems.  All these issues mean that being overweight or obese results in financial repercussions in increased healthcare expenses.  Can we reduce these costs with a simple diet pill?

Experimentation with concoctions to reduce weight have been tried for centuries with examples such as laxatives, arsenic and amphetamines.  Yet all of these have a limited effect and most have serious side effects.  Diet drugs are developed using the principle that weight gain or loss depends simply upon whether energy uptake is equal to the output.  Various methods can be used to encourage weight loss:

1.  To reduce energy uptake, drugs can be used to block food from being absorbed from the gut (e.g.  Orlistat can be used to block the uptake of fat).

2.  To reduce energy uptake, appetite can be suppressed therefore decreasing the volume of food consumed (e.g. amphetamine-based drugs or anorectics)

3.  To increase energy output, drugs can increase activity levels or increase an individual’s metabolic rate, burning more calories.

Diet pills need to be extensively tested for possible side effects and toxicity because healthy individuals will end up taking them for cosmetic reasons and they therefore cannot be allowed to make people ill.  This is one of the reasons why we are still missing an effective weight loss pill because they have to be so thoroughly tested and controlled.

Amphetamines

In the 1930s, amphetamines were by far the most popular diet drugs on the market.  These included a broad range of drugs which acted as stimulants.  They reduced appetite and increased activity levels.  However in the US only one amphetamine-like drug remains on the market: phentermine.  This is because Amphetamines are highly addictive and have been associated with neural-toxicity, psychosis and have been shown to cause heart valve problems.

Orlistat

Orlistat reduces fat absorption by acting as an inhibitor for pancreatic lipase.  This works well as a diet drug as obesity is commonly caused by a high fat diet.  Side effects of this drug include flatulence and incontinence, although decreasing the fat content of the diet can reduce these symptoms.  Orlistat has also been seen extremely rarely to cause severe liver damage.  Orlistat is currently the most common weight loss pill on the market.

Qnexa

This is one of the most effective diet pills on the market with results from a year long trial, showing that on average people lost 9.3% of their body weight after accounting for the placebo effect.  It came on the market in September 2012.

Loracaserin

Made by Arena Pharmaceuticals in California, loracaserin reduced appetite.  It does this by binding to serotonin receptors in the brain.  It has very few side effects and is seen as a relatively safe weight loss drug.  The downside to this drug is that it has only a mild weight loss effect with the results of a trial showing that on average people lost 3.6% of their body weight after accounting for the placebo effect.  It came of the market in late June 2012.

New diet drugs that come on to the market are now seen with skepticism.  Doctors are careful about prescribing diet pills except as a last resort for obese people with serious medical conditions such as type 2 diabetes.  David Ludwig, an obesity doctor at Harvard Medical School summarizes this view, “Each of the dozens of drugs previously proposed initially carried great excitement, before their limitations became clear”.