Quantity and pace of weight loss vary significantly from peron-to-person, so figures of average monthly weight loss on phentermine only provide a general estimate for each patient's true weight loss potential. Starting weight, pre-existing medical conditions, genetics, diet, physical activity and other factors all affect patients' individual phentermine weight loss results. While some people report losses of over 20 pounds per month, others struggle to drop even one pound per week. Still, despite the wide range of actual phentermine results (and reviews), most people do lose more weight with phentermine than without it.
Phentermine acts as a central nervous system stimulant to promote weight loss. It creates a biological response similar to “fight or flight” that promotes weight loss because, as part of the heightened state, appetite decreases and energy increases. This combination of effects helps patients eat less and move more to promote healthy weight loss .
Still, phentermine is not a miracle pill. This medication should always be combined with healthy lifestyle changes to achieve best results.
Phentermine expected weight loss is ≥5% of body weight in three months . This translates to a predicted weight loss of at least 10 pounds for someone with a starting weight of 200 pounds, or at least 12.5 pounds for a person who starts at 250 pounds.
|Starting Weight (Pounds)||Short-Term Goal (-5%)||Pounds to Lose|
While these modest weight loss goals may seem disappointing to some ambitious dieters, it is healthier (and more sustainable) to lose weight slowly and steadily as opposed to quickly and dramatically . This medication is also designed for limited, short-term use, which limits the amount of weight an individual can healthfully lose.
Phentermine is FDA-approved as a "short-term treatment" for exogenous obesity, meaning that it should not be taken for more than 12 weeks at a time [4,5]. Still, rapid or extreme weight loss is NOT the goal. If patients have more weight to lose than proves realistic in 12 weeks' time, many doctors will prescribe phentermine off-label for longer periods of time, or give patients with multiple rounds of treatment punctuated by 1-2 month breaks between periods of active treatment.
Average weight loss per week on phentermine is about 1-4 pounds, based on both clinical research and user reviews. Studies indicate weekly weight loss tends towards the lower end of this range, while online user reports indicate more rapid weight loss remains common. Either way, a healthy, calorie-reduced diet plus regular, doctor-approved physical activity help maximize weight loss on phentermine.
How much weight is that?
A 15 oz can of beans weighs about one pound.
Weight loss varies significantly between individuals, but research shows that phentermine users can expect tolose about 3-5 pounds per month [6-8]. This is a healthy rate of weight loss that allows the body to burn fat while also maintaining valuable lean muscle tissue . Still, user reports indicate that many patients lose closer to 5-10 pounds per month, or even more . Younger, heavier and more active patients tend to lose weight faster than their older, lighter or more sedentary counterparts.
How much weight is that?
One standard bag of potatoes weighs about 4 pounds.
This medication's effects are strongest at the beginning of treatment, so average weight loss in the first month of phentermine use is greater than weight loss in subsequent months. Patients often experience stronger appetite suppression and more energy in the first couple of weeks of their prescription, both of which facilitate greater weight loss. Another reason patients drop pounds faster in the first month is a loss of water weight. When someone falls into a calorie deficit – due to eating less, exercising more, or a combination of the two – glycogen is the first fuel that the body draws on to sustain itself. However, in addition to easily-accessible energy, glycogen also contains a high percentage of water. So, at the beginning of patient's weight loss journey, when he/she begins burning through their glycogen stores, it is common to see a significant drop on the scale due to the loss of glycogen-related water weight . This drop-off effect is most noticeable in people who were not dieting or otherwise creating a calorie deficit before starting phentermine.
Yes, it is possible to lose 20 pounds a month on phentermine, but the average user does not achieve this striking weight loss.
Individuals that report rapid, dramatic weight loss on phentermine are usually in their first month of treatment and have committed to major lifestyle changes alongside the medication. Sarah, for example, focused on healthy eating, proper hydration and regular activity during her post-partum phentermine journey. She lost an impressive 22 pounds in just one month!
In one study, patients who took 37.5 mg of phentermine HCL – combined with a 1500 calorie/day diet – lost an average of 16 pounds in 3.5 months, or just under 5 pounds per month . Another study found that phentermine hydrochloride alone – without any special diet or exercise plan – also produced an average weight loss of about 8 pounds in 3 months, or about 2.67 pounds per month. Results of this second study, however, displayed significant variation with some patients losing no weight, and others (especially younger subjects) losing more than 16 pounds in that same timeframe .
How much weight is that?
A gallon of milk weighs about 8.6 pounds.
Users who have taken phentermine off-label for 6 months of continuous treatment, or who have used 2 separate rounds of phentermine with a break in-between, self-report an average weight loss of around 55 pounds . When broken-down, that is an average loss of just over 9 pounds per month.
How much weight is that?
5 medium-sized bowling balls weigh about 50 pounds.
In a 1968 study, patients treated with 30mg phentermine resin (Duromine) - either consistently or intermittently - plus a low-calorie diet lost an average of 27 pounds in nine months . That converts to about three pounds per month, or about 36 pounds per year.
However, based on more recent phentermine before and after stories submitted online, the average phentermine weight loss in one year is closer to about 65 pounds, or a little over 5 pounds per month .
How much weight is that?
The average car tire weighs 22 pounds.
The combination of two medications - phentermine and topiramate - is one of the most effective prescriptions for weight loss . This pair is available either individually as generics or combined into one capsule as the brand-name pill, Qsymia.
A 2012 study found that patients who took the highest dose of phentermine-topiramate (15 mg phentermine HCL + 92 mg topiramate-ER daily) lost significantly more weight than those who took a lower dose of phentermine-topiramate or a placebo. In fact, subjects taking the highest dose of phentermine-topiramate lost almost 11% of their starting body weight over the course of the 56-week trial (as compared to 5% and 1.5% in the lower dose and placebo groups, respectively). Given that the starting weight in this group was an average of 253 pounds, that translates to an almost 28-pound weight loss in just one year !
A subsequent study in 2016 supported these results, reporting that over 75% of patients on combined phentermine and topiramate treatment lost at least 5% of their body weight during the one-year trial period .
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