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Does Phentermine Speed Up Metabolism?

author image Andrea Cespedes
Andrea Cespedes is a professionally trained chef who has focused studies in nutrition. With more than 20 years of experience in the fitness industry, she coaches cycling and running and teaches Pilates and yoga. She is an American Council on Exercise-certified personal trainer, RYT-200 and has degrees from Princeton and Columbia University.
Does Phentermine Speed Up Metabolism?
Phentermine is used only for a short time to prompt faster weight loss. Photo Credit: KatarzynaBialasiewicz/iStock/Getty Images

Doctors may prescribe phentermine to expedite weight loss when combined with a low-calorie diet and a more active lifestyle. Phentermine is used only for a short time to prompt faster weight loss, especially for patients preparing for weight loss surgery or whose overweight status immediately endangers their health. Phentermine suppresses the appetite, so it's easier to resist cravings and not overeat. It does not directly increase metabolic rate, however.

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How Phentermine Works

Phentermine is known as a sympathomimetic agent, which mimics the activity of the chemical norepinephrine, which is a naturally occurring chemical in the brain. Phentermine acts as a stimulant on the brain and suppresses the appetite. Some people experience a "high" from phentermine -- so much so that phentermine is sometimes sold on the black market.

Doctors prescribe phentermine for three to six weeks at a time, but usually not longer than 12 weeks. Depression and increased blood pressure are possible side effects. A doctor monitors anyone taking the drug, as phentermine can be habit forming.

Taking Phentermine

A doctor may prescribe tablets or extended-release capsules. The drug is taken as a single dose first thing after waking or 30 minutes before meals. It is important to follow a doctor's prescription exactly. Never take more than the prescribed dose or take the pills more frequently than directed.

Anyone taking phentermine who experiences heart palpitations, dizziness, insomnia, shortness of breath or any other unusual or disturbing symptoms, contact the doctor or call 911 immediately.

Eating While on Phentermine

Doctors should provide patients with dietary guidelines to follow while they're on phentermine. A low-calorie plan that involves eating moderate portions of lean proteins, whole grains, watery, fibrous vegetables and fruits assists with weight loss. The appetite-suppression qualities of phentermine makes people less hungry than usual and these qualities also help with cravings for sugary sweets and fatty foods.

Exercise and Phentermine

It's important to follow all exercise guidelines recommended by the doctor. Sometimes people find that exercise performed before taking phentermine is difficult now or causes shortness of breath. If that happens, stop exercising immediately and contact a doctor.

Phentermine is not connected to the heart problems associated with the now-banned weight-loss drug called Fen-Phen, which was a combination of phentermine and fenfluramine. Phentermine has been approved by the U.S. Food and Drug Administration since 1959. When used properly, phentermine is relatively safe.

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