Disclaimer: None of the information in this article constitutes medical advice, and is just the opinion of the writer(s). We recommend that patients follow their doctor’s guidance in regards to prescription medication.
Phentermine is a prescription medication for weight loss. It’s one of the most popular doctor-prescribed treatments for obesity in the U.S.
In this article we’ll review medical studies on phentermine to determine if it’s likely to be safe and effective for weight loss, as well as provide some natural alternatives which may be as effective with fewer side effects.
How Does Phentermine Work?
This drug works primarily through appetite suppression. When patients take phentermine pills, their levels of norepinephrine increase significantly. This neurotransmitter has indirect effects on hunger.
Phentermine is thought to work by inhibiting expression of a neuropeptide which signals the body of hunger, based on medical research, but the exact mechanism of action isn’t fully understood.
What we do know is that phentermine has a similar molecular structure to amphetamine, and has similar effects such as central nervous system stimulation and increased heart rate and blood pressure.
Is Phentermine Effective for Weight Loss?
Medical research shows that phentermine is effective for weight loss, both short-term and long-term.
A medical trial on an obese Korean population found that, over 14 weeks, nearly 90% of the patients taking phentermine lost 5% of body weight or more, and 50% of patients taking phentermine lost 10% of body weight or more. This would be categorized as a short-term trial.
These figures were significantly higher than the placebo group, of which 17% lost 5% of body weight or more, and 8.3% lost 10% of body weight or more.
This study proved that phentermine was around 5 times more effective than placebo.
A separate study analyzed the safety and effectiveness of long-term phentermine use, up to 24 months continuously. It found that patients taking phentermine for over 12 months lost 7.4% more weight than a reference group that wasn’t taking the drug.
We can conclude that phentermine works for weight loss in the context of both short-term and long-term use.
Phentermine Side Effects
Phentermine seems relatively safe compared to other weight loss pills we’ve reviewed like Contrave.
Adverse cardiovascular events like a heart attack would be the biggest concern with a drug of this type, since it primarily acts as a nervous system stimulator. However, the long-term study linked above found no increased CVD or death risk in the phentermine group compared with the reference group. It’s important to note that the study participants were classed as “low-risk” without any pre-existing conditions like high blood pressure.
Another study on 932 obese adults who took phentermine for three months found no increased cardiovascular risk.
Some of the most common side effects of phentermine according to LiverTox are: anxiety, palpitations, headache and insomnia. While these side effects aren’t life-threatening, they can be uncomfortable.
Since phentermine is very similar to amphetamine, the side effect profile is similar. It’s a stimulant, and stimulants can engage the fight-or-flight response in our bodies.
While we don’t find the side effects of phentermine to be especially concerning, use of this drug does seem risky compared with natural weight loss treatments which carry no side effect risk.
Natural Weight Loss Alternatives
Lifestyle changes are the most effective long-term weight loss strategy, and we want to highlight a unique dietary strategy that’s proven in medical studies but isn’t discussed enough in weight loss review articles.
Increasing intake of dietary fiber has been consistently shown in medical research to predict weight loss. This sounds crazy but it makes sense logically. Fiber is indigestible plant material. This means that it takes up space in the stomach without increasing caloric intake, making people feel full faster.
This is why eating 1,000 calories of McDonald’s burgers is easy, but eating 1,000 calories of beans, rice and vegetable stir fry is more of a challenge. The healthier meal has much more fiber.
The amazing thing about fiber intake as a weight loss mechanism is that it has a dose-dependent effect (as proven in medical data), meaning that the more fiber you eat (to a limit), the more weight you lose.
It’s best to slowly increase fiber intake because switching from a low-fiber diet to a high-fiber diet can cause some transient gut discomfort like bloating and increased gas.
Fiber can be found in both foods and supplements, and both soluble and insoluble fiber are beneficial for weight loss. Here are some healthy food and supplement options for increasing fiber intake:
Beans are the ideal healthy high-fiber food, as they’re very cheap and also high in minerals like potassium and magnesium. We recommend buying dried beans over canned beans as they’re cheaper and have no BPA risk from the cans.
Oats have been found to contain a specific type of fiber called beta glucan which can reduce cholesterol. They’re very cheap when purchased in bulk, and we recommend steel-cut oats over instant oats as they have a lower glycemic index which means less impact on blood sugar levels.
Berries are another healthy high-fiber option, and contain high levels of Vitamin C as well. We recommend frozen or fresh berries over dried berries, which have a higher glycemic index.
Psyllium Husk is a fiber powder you can purchase as a supplement, and has been associated in medical research with a wide range of beneficial health effects.
All of these food products can not only help you lose weight, but can make you feel better through improved overall health. We always recommend natural, non-toxic solutions over pharmaceutical drugs as a first measure.