Stimulant drugs that increase metabolic rate, such as amphetamines, are often effective for promoting weight loss, but can be associated with a high risk-to-benefit ratio. As a result, numerous prescription as well as over-the-counter stimulants have been withdrawn or strictly limited to short-term use with small populations of individuals, leaving few prescription medication options available.
Patients and doctors seeking safe, effective metabolism-enhancing weight-loss alternatives may find satisfactory solutions through certain naturally-occurring substances found in some common foods. These provide a gentle energy-burning boost, while avoiding many of the health hazards of harsh stimulants.
Phentermine and Topiramate
Phentermine, a central nervous system stimulant, prompts the brain to release the neurotransmitter noradrenaline in a similar manner to amphetamines, but is not addictive. Some phentermine patients have also been reported to continue to lose weight after stopping the drug.
Because of its stimulant properties, patients with irregular heart rhythm, high blood pressure or hyperthyroidism should not take this medication. Similarly, monoamine oxidase inhibitors and other drugs that affect the central nervous system, such as decongestants, should not be used concurrently with phentermine. Its high risk profile, mainly related to high blood pressure and other vascular disorders has caused phentermine to be withdrawn in some countries.
To take advantage of the benefits of phentermine while mitigating its health risks phentermine has been combined successfully with a drug called topiramate. Designed to prevent seizures, topiramate has also been found to promote weight loss, possibly by suppressing compulsive food cravings. Additionally, topiramate is thought to increase energy expenditure by inhibiting fat and glycogen production and making the body less efficient at conserving energy.
Side effects of topiramate include:
- numbness and tingling
- altered taste sensation
- increased risk for kidney stones
- decreased sweating
- fatigue and sleepiness
- dry mouth and constipation
Topiramate may also cause depression, impaired concentration and memory, and blurred vision.
In phase 3 clinical trials of phentermine/topiramate the combination drug resulted in an average of up to 10.6% body weight loss over the course of a year. In a one-year continuation of that study 78% of volunteers elected to remain on the drug. Results showed the original weight loss was successfully maintained. Currently, this drug is not approved by the TGA and is not available as a combination product in Australia.
Green tea
The same compounds in green tea that give it powerful antioxidant and anticancer benefits also make green tea a healthy addition to a weight loss program. Known as catechins, these compounds provide a mild metabolic boost that increases fat burning without the dangerous side effects of stimulants. Catechins also decrease fat absorption, suppress appetite and inhibit enzymes required for the production of fat.
A review of previously published research found that green tea catechins decreased body weight by an average of 0.44 kg. When combined with caffeine, a weight loss of 1.38 kg occurred. Other studies have found that green tea provided modest, but insignificant weight loss with one study also concluding that green tea failed to maintain weight loss over time.
Cayenne pepper
Capsaicin, the active compound that gives chilli peppers their spicy flavor, also boosts metabolic rate by up to 50 calories per day and particularly favors the burning of fats for energy. Additionally, capsaicin has an appetite-suppressing effect. In one study, chilli consumption increased fat-burning between meals by 7%.
Some studies have concluded that capsaicin may increase risk for stomach cancer while other studies have not found an increased stomach cancer risk. Capsaicin has been found to have greater fat-burning benefits when consumed with food than when taken in capsule form. However, with regard to appetite suppression, some studies show that long-term use of chilli pepper may result in desensitization and diminishing results, though metabolic benefits are maintained with regular use.
Citrus aurantium
Commonly known as bitter orange, this citrus fruit contains a compound called synephrine that acts as a stimulant. Bitter orange is increasingly appearing in weight-loss formulations as a substitute for ephedrine, which has been banned in Australia due to its high side-effect profile. Citrus aurantium has been shown to induce significant weight loss in the second and third weeks of dieting, when weight loss typically slows following the initial loss of water-weight in the first week. Synephrine is also found in other citrus fruits as well as other foods consumed daily by many people and is considered by some experts to be exceedingly safe. In a review of previously published studies that included 360 volunteers, bitter orange elevated resting metabolic rate and energy expenditure and produced modest reductions in weight with no reported adverse events. Blood counts and urine analysis also remained unaffected after up to 12 weeks of bitter orange use in these studies.
Garcinia cambogia
This small pumpkin-shaped tropical fruit has garnered attention in recent years for its purported weight loss benefits. In a laboratory animal study, Garcinia cambogia significantly reduced body fat and inhibited fat accumulation without decreasing food intake. It also reduced levels of resistin, a hormone produced by adipose cells that promotes insulin resistance and is associated with obesity.
Expert opinions vary with regard to the safety of Garcinia cambogia. Some studies have found that long-term use may lead to liver damage, inflammation and oxidative stress. In obese laboratory animals with fatty liver deposits, Garcinia cambogia increased formation of scar tissue in the liver. The supplement also increased levels of certain liver enzymes and inflammatory markers as well as levels of antioxidant enzymes, all of which indicate stress on the liver.
Some researchers assert that claims of Garcinia cambogia's liver-damaging side effects are unwarranted and arise from flawed studies, stating that, to the contrary, the supplement reduces inflammation in the brain, intestines, kidneys and blood and may provide protective, or, at worst neutral effects on the liver.
A study published in 2012 found that, though no long-term safety studies had been conducted in humans, researchers could find little evidence to prove its effectiveness beyond 12 weeks. Likewise, significant toxicity had not been proven at typical dosage levels.
References
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- http://www.pbrc.edu/training-and-education/pdf/pns/PNS_Green_Tea.pdf
- http://ajcn.nutrition.org/content/91/1/73.long
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