Does Phentermine Burn Fat or Just Suppress Appetite?

Medically reviewed by Dr. Paul Hetrick, PharmD, this article explains how phentermine supports weight loss, whether it directly burns fat or mainly suppresses appetite, and what to expect during treatment.

What is Phentermine?

Approved by the FDA in 1959, phentermine is a prescription medication used for short-term weight management. It’s prescribed to adults with a BMI of 30 or higher, or 27+ with weight-related conditions like high blood pressure or diabetes. Available as Adipex-P, Lomaira, and generics, it acts mainly as an appetite suppressant and CNS stimulant.

Does Phentermine Burn Fat or Just Suppress Appetite?

While phentermine primarily suppresses appetite by increasing neurotransmitters like serotonin, noradrenaline, and dopamine, it indirectly supports fat burning. Its stimulant effects boost energy and activity levels, encouraging your body to break down stored fat for energy, though it does not directly burn fat.

How Quickly Can You Lose Weight on Phentermine?

Studies show most users lose at least 3% of their body weight in 12 weeks. On average, people may lose around 4.4% more weight than placebo after 28 weeks, with some losing up to 13% of body weight after 36 weeks. Individual results vary based on lifestyle and metabolism.

What to Expect if You Take Phentermine

Dosage and Administration

Phentermine is taken orally in tablet or capsule form, typically once daily before breakfast or 1-2 hours after. Common doses include 37.5 mg for Adipex-P and Lomaira, and 8 mg for Lomaira tablets, with adjustments based on individual response.

Effects and Feelings

It stimulates the central nervous system, leading to increased energy, alertness, and sometimes jitteriness or restlessness. Side effects like dry mouth, insomnia, and constipation are also common but manageable with hydration and fiber intake.

Benefits of Taking Phentermine

• Appetite suppression leading to reduced calorie intake
• Increased energy and activity levels
• Rapid initial weight loss, motivating continued efforts
• Supports fat loss indirectly through increased activity

Side Effects and Warnings of Phentermine

Common side effects include dry mouth, insomnia, jitteriness, and increased heart rate. Serious risks involve chest pain, heart palpitations, swelling, pulmonary hypertension, and potential dependency. It’s contraindicated for individuals with certain health conditions.

When Not to Take Phentermine

People with heart disease, high blood pressure, anxiety, pregnancy, breastfeeding, glaucoma, or a history of substance abuse should avoid phentermine. Always consult a healthcare provider to evaluate safety based on your full medical history.

Alternatives to Phentermine

If phentermine isn’t suitable, other appetite suppressants and weight loss medications like Wegovy, Xenical, Contrave, and Qsymia may be options. Discuss these alternatives with your healthcare provider to find the best fit for your needs.

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Medical Disclaimer

The information provided here is for educational purposes only and does not substitute professional medical advice. Always consult your healthcare provider before starting or stopping any medication, and discuss your full medical history to ensure safety.

FAQs about Phentermine