The pounds are starting to pile up. The sensible exercise regime and clean diet that worked in the past seem to have lost their effectiveness.

The horror. Perhaps you are getting old and your metabolism is slowing down, so you decide it is time to get some help. With the array of weight-loss supplements out on the market, how should one decide what to pick off the supplement store shelves?

APPETITE REDUCERS

Hoodia

African bushmen would eat hoodia while going on long hunts where food and water would not be available for days. Hoodia tricks the brain into thinking that it is full through an unknown mechanism, which may also suppress thirst. This is potentially dangerous, so those on hoodia have to make a conscious effort to drink water. It is also unknown how safe hoodia is.

Fibre

Besides improving bowel movements, products that are high in fibre, like psyllium, pectin and guar gum, create a sense of fullness so one will eat less. Fibre works by absorbing fluid to expand in the stomach.

Just take note to increase fibre intake gradually and drink more water, or else constipation could result.

METABOLISM BOOSTERS

Simulants or thermogenics

These stimulate the nervous system to increase a person's metabolic rate. This in turn causes more calories to be burnt, especially during exercise.

Caffeine is an example of a stimulant. A cup of coffee contains between 80 to 135mg of caffeine, or you could also get it from guarana, a type of Brazilian bean.

Guarana has twice the amount of caffeine in coffee and is therefore a popular ingredient in thermogenic supplements. Research suggests guarana is an effective energy tonic, increases mental acuity and enhances physical endurance under stress.

There is also green tea, which offers thermogenic properties with just a small caffeine boost - about 15mg. This makes it useful for those who are unable to tolerate caffeine, or who are on medication as caffeine is known to interact with some drugs.

Yerba mate

This South American herb contains caffeine and has appetite-suppressing, pain-relieving and fat-burning properties. But be warned: yerba mate consumption has been associated with increased risk of some cancers, like those of the lung, kidney and bladder.

Synephrine

Also called bitter orange or citrus aurantium, synephrine has become popular as an alternative to ephedrine (which was banned in 2004 after several deaths related to its use were reported). Synephrine been shown to metabolise fat in very high doses, but the downside is that it increases blood pressure and also the risk of cardiovascular problems.

It may also result in sleeplessness, headaches and dizziness and interact with medicines, so it is best to seek a doctor's advice before using.

To read more about these weight-loss supplements as well as others like fat burners, fat absorbers and carb blockers, grab a copy of this month's Men's Health.