What's the skinny on diet pills? How do they work?

23 January 2012

If you go to your local drug store or health foods store, you'll notice there is a whole whack of diet pills out on the market, from herbal supplements to prescription medications, and each work a little differently depending on what ingredients they contain.

Prescription Diet Pills

One of the most common types of diet pills are those that suppress the appetite. These pills contain compounds such as sibutramine, diethylpropion and phentermine which work on the tiny region of the brain called the hypothalamus - the appetite controlling area of the brain.

The hypothalamus responds to the chemical messengers serotonin and norepenephrine which regulate the feeling of satiety (or feeling full). By preventing the removal of these messengers, these compounds are able to keep sending their signals, leaving you feeling fuller longer and therefore causing you to eat less.

Fact: Serotonin is an example of a neurotransmitter which also helps regulate sleep and temperature. Along the same lines are diet pills that control food cravings. One example is the compound rimonabant which blocks the function of the proteins in the brain called endocannabinoids.

Endocannabinoids are naturally produced by the body and interestingly, are similar in structure to the active ingredient in cannabis or marijuana. These molecules have been shown to stimulate appetite so preventing their action can help ward off "the munchies"

Did You Know?
About one-half of teenage girls (one in every two) and one-quarter (one in every four) of teenage boys have tried dieting to change the shape of their body Another other type of diet pills are ones that block the breakdown of fat. The active component in these pills is the compound orlistat which blocks the activity of the enzyme lipase (a fat-degrading enzyme).

But why would you want to prevent fat from being broken down? Wouldn't it make sense to get rid of the fat to lose weight? Well that's just what orlistat does.

After we consume foods containing fat, the fat is normally broken down in the intestine by lipase which then allows the fat to be absorbed by the body. By inhibiting lipase, some of the fat that is ingested gets removed through the feces instead, helping to eliminate the fat from your body.

Did You Know?
More than one in three girls (about 33%) who are actually at a healthy weight try to diet. Herbal Diet Pills

Herbal diet pills are commonly labelled as "all natural" since they contain ingredients which are naturally found in nature. For example, diet pills containing caffeine are thought to increase your body's metabolism by speeding up the breakdown of fatty acids.

However, only a few studies have shown that consuming large amounts of caffeine may have an effect on weight loss but no studies showed that the effects were significant or permanent.

Others common natural ingredients in herbal diet pills include guar gum and psyllium (which help create that "I'm full" feeling), green tea and pyruvate (which help slow down fat production) and chitin (which helps prevent fat from being absorbed).

But diet pills aren't an easy or safe answer to weight loss problems. Many have been shown to have harmful side effects, including elevated blood pressure, nervousness, diarrhoea and even heart failure!

In general, a healthy lifestyle and proper exercise helps control and maintain a healthy weight. So if you are considering diet pills to help shed some weight, you should consult your doctor first.

Learn More!

TeensHealth (Nemours Foundation)

Canadian Health Network: Click on "youth".

The National Eating Disorder Information Centre (NEDIC)

Canadian Paediatric Society's Healthy Active Living Program


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