The Effects of Phentermine on Weight Loss

Dr. Christopher McGowan
April 5, 2022

Most weight loss plans involve a revised diet and an increase in one’s daily physical activity in order to create a fat-burning calorie deficit. The unfortunate truth is, though, that diet and exercise alone rarely lead to long term success. Indeed, recent research from the CDC indicates an increase in the number of people attempting to lose weight at the same time as body mass index (BMI) and obesity-related diseases have continued to increase. One way doctors are trying to reverse this trend is through medication like phentermine.

What is Phentermine?  

Also known by the trade names Adipex-P and Lomaira, phentermine is a prescription medication that is primarily used as an appetite suppressant (anorectics). Like many other medications used to treat obesity, phentermine is intended to be used as a supplement to a weight loss plan. It is most beneficial for obese individuals who haven’t been able to lose sufficient weight through diet and exercise alone. It may also be used by those who have a BMI over 27 with an obesity-related condition like high blood pressure or type 2 diabetes. 

Phentermine is intended only for short term use and is typically prescribed for up to 12 weeks at a time. As a sympathomimetic drug, phentermine affects the sympathetic nervous system and the body’s fight or flight response. In this way, it is somewhat similar to the stimulating effect amphetamine has on the central nervous system. Like with amphetamines, the use of phentermine can potentially lead to dependence. Though the risk of addition is fairly low, it is nevertheless categorized as a Schedule IV controlled substance. 

Originally approved for use by the Food and Drug Administration (FDA) in 1959, phentermine began being prescribed as a combination with fenfluramine (or dexfenfluramine) called fen-phen. After numerous cases of related heart valve problems, fen-phen was taken off the market. Today, phentermine is still available by itself as an appetite suppressant, though it is sometimes combined with the anticonvulsant topiramate as well; this combination is marketed as an obesity treatment called Qsymia. 

How Does Phentermine Work? 

As a type of anorectic drug, phentermine works to suppress the appetite by stimulating the release of certain neurotransmitters in the brain. By triggering the release of norepinephrine, dopamine, and serotonin, the drug neurochemically reduces your perception of hunger and so you feel full and eat less. By its very nature, phentermine can only help a person indirectly by curbing hunger and cravings; outside of a diet plan, it has very little chance of making a difference to someone’s weight loss process.   

How Effective is Phentermine for Weight Loss?     

As with other weight loss drugs (and essentially all weight loss programs), the effectiveness of phentermine is largely dependent on your starting excess weight and the modifications to your diet. Research has shown that it can be effective to an extent; two small studies in South Korea, for instance, found that over 80% of the subjects lost at least 5% of their body weight after a 12-week course of phentermine. For a 300-lb man, that would equate to approximately 15 pounds lost. 

Common Side Effects of Phentermine   

Though phentermine does have some known side effects, one of the reasons it’s still a popular appetite suppressant is because those side effects are typically mild and short lived. This is at least in part because the effectiveness of the drug itself only lasts a short time and is the main reason it is prescribed for only up to 12 weeks. After that, most people build up a tolerance to the drug that doesn’t improve until the patient has taken an extended break. Below is a list of some commonly reported side effects: 

  • feeling of restlessness
  • difficulty sleeping
  • headaches
  • dry mouth 
  • nausea 
  • constipation
  • diarrhea 
  • heart palpitations
  • high blood pressure
  • tremors
  • change in libido  
  • tingling in the hands or feet 

Who Should Avoid Phentermine?  

Phentermine, like most types of weight loss medication, is relatively safe, but it isn’t for everyone. For instance, it isn’t usually prescribed for people who have a BMI lower than 27 and who haven’t already attempted to lose weight through other means. Additionally, though, doctors recommend phentermine be avoided by those with certain health statutes or conditions like: 

  • heart disease 
  • an allergy to similar stimulants
  • high blood pressure 
  • hyperthyroidism 
  • being pregnant or breastfeeding an infant 
  • a history of drug abuse or misuse 
  • significant anxiety or nervousness
  • glaucoma

Alternatives to Medication

If you’re already on a weight loss journey and looking for an additional edge to keep hunger under control, phentermine can be helpful. Even though it is only prescribed for a short time, the appetite-suppressing nature of phentermine can promote longer term dietary habits that lead to sustained weight loss. Yet medication isn’t the best option for everyone, and some people with certain conditions aren’t good candidates for a prescription.

Sustained, long term weight loss is often elusive for many people, and there are a wide variety of reasons why people fail, including genetics, food availability, and various environmental factors. That’s why at True You Weight Loss we are passionate about helping people find the freedom they’ve been looking for in their journey by offering a series of state-of-the-art non-surgical weight loss procedures. Since our procedures are done endoscopically, no incisions are required; this means a much lower chance of surgical complications as well as a shorter recovery time. 

As noted above, phentermine studies showed that most people had about a 5% reduction in body weight as a result of taking the medication. By comparison, patients who have had True You’s ESG procedure, for example, lost an average of 20% of total body weight or 70% of their excess weight. Moreover, patients who had the procedure also saw marked improvement in blood pressure, blood sugar, and a number of other obesity-related problems. Below are some of True You’s most common procedures:     

  • ESG: In an endoscopic sleeve gastroplasty, an endoscope is lowered down the esophagus and into the stomach. Once there, special tools mounted on the endoscope are used to reshape the stomach from the inside. When complete, the stomach will have been reformed into a smaller, sleeve-like shape that has 20% of the previous volume. The permanent reduction in stomach volume promotes weight loss by making you feel full sooner since the stomach can’t hold the same amount of food.
  • Gastric balloon: True You offers two different types of gastric balloon: Spatz3 and ORBERA®. Though the two types have some differences, the basic principle is the same. Via endoscope, a deflated silicone balloon is placed in the stomach and filled with a harmless saline solution. Once in place, the balloon takes up space and similarly causes you to feel full sooner than you normally would and promote weight loss. 
  • Revision: Some people have already had gastric bypass surgery or a sleeve gastrectomy but the effectiveness of the procedure has started to wane. In these cases, an endoscope can be used to modify the original surgery to make it similarly effective again. 

Contact True You Weight Loss Today

Losing weight is an elusive goal for many Americans, but it doesn’t have to be. At True You, we understand the journey and how challenging it can be sometimes. If you would like more information about your weight loss journey or endoscopic procedures, please contact us today to request a consultation. Freedom is waiting!

Dr. Christopher McGowan
Dr. Christopher McGowan
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