I approach obesity as an addiction, … addiction to food.

Obesity is a result of eating more than what the body needs … the balance is stored in the body as fat for future use. This genetic trait of storing energy as fat helped our hunter gatherer ancestors survive.

But we are not hunter gatherers any more. At the most we have to gather food from the nearest 24 hour food store, where fruits, vegetables, meats, and grains, come in neat little packages. And if we so choose … we may get it precooked, delivered to our home.

Our hunting is now limited to gathering our fellow hunters and hunting for a restaurant where we can chose what to eat, without risking our life or limb.

Obesity results from having abundant choice … readily available food, enhanced to appeal to our sight, smell, and taste, and brought to us by home delivery … coupled with our sedentary life, resulting in a serious imbalance of energy consumed vs energy needed and actually spent. Our body does what it is supposed to do … it stores this excess energy as fat.

The human physiology evolved for hunter gatherers … we need to alter our habits to adapt this physiology to our modern sedentary life.

Obesity is harmful … it increases risk factors for several diseases … high blood pressure, heart attacks and stroke, diabetes, sleep apnoea, low back pain, osteoarthritis, and it increases risk for injuries.

Obesity has professional, social and emotional effects. It results in disqualification from certain jobs, contributes to poor self image, and adds to depression.

Obesity shortens our life, makes it less enjoyable, and adds to healthcare costs. It can be prevented and cured.

Prevention is better than cure … but cure is still the second best, … even partial cure will give significant health benefits.

How Naltrexone helps in treating Obesity?

A new medication called “Contrave” was approved by FDA in 2014 for the treatment of obesity. Contrave is a combination of two older medications, the opioid blocker Naltrexone, and the antidepressant Bupropion.

The exact mechanism of action of this combination is not known, but it has shown to reduce craving for food.

Naltrexone is an opioid receptor blocker. Opioid receptors have been implicated in the neuro-chemical pathways that determine pleasure, reward, and habit formation. Naltrexone is used in the treatment of alcohol and opioid addiction.

Bupropion, commonly known as Welbutrin and Zyban, acts as a nicotinic receptor blocker, and increases the availability of Norepinephrine and Dopamine in the brain. It is an inexpensive and popular atypical antidepressant that does not cause sedation or weight gain. It is also used for smoking cessation.

Consumer Reports did an analysis of the effectiveness of Contrave and came to the conclusion that the weight loss from Contrave was not significant enough and that it came with high incidence of risks.

In addition Contrave (Naltrexone+Bupropion) was found to be less effective than Qysmia (Phentermine+Topiramate) in effecting weight loss.

It is true that the weight loss results from Contrave have not been spectacular, however, that has been a problem with all weight-loss drugs, none of them are spectacular, … and all come with their own set of problems, and side effects. Side effects are a bigger problem when medications are used in higher doses and for a longer duration.

The high incidence of the side effects and risks of Contrave are mostly attributed to its Bupropion component, and are dose related. On the other hand, Bupropion was approved in 1985 and is a widely used antidepressant and smoking cessation drug. Some unacceptable risks mentioned are suicidal ideation and seizures. The possibility of suicidal ideation is common to most antidepressant drugs, and is a significant component of depression itself. Risk of seizures is very low and can be reduced by careful patient selection and lowering the dose.

My method to treat obesity is to start with Naltrexone. If that does not get reasonable weight loss then I prescribe Naltrexone and Bupropion independent of each other, and customize the dose based on results and side effects.

Rationale for using Naltrexone for weight loss?

First of all Naltrexone by itself is not approved for weight loss, and this is an off label use of the medication. FDA approval for specific indication is based on application by manufacturers. There may not be enough financial incentive to get Naltrexone approved for the indication of weight loss.

Second there are better medications for weight loss, … medications that have been approved by FDA for weight loss are Qysmia, Belviq, Contrave, Phentermine, Orlistat, etc.

FDA approved medications for weight loss are not useful for someone who can not take those medications. Reasons could be; contraindication due to specific medical conditions, unacceptable side effects, higher costs, or cumbersome insurance requirements.

The pharmacological basis for prescribing Naltrexone is:

  1. Naltrexone is an approved component of a weight loss medication Contrave.
  2. Naltrexone is an opioid receptor blocker. Opioid receptors have been implicated in the neurochemical pathways that determine pleasure, reward, and habit formation.
  3. We are programmed to respond to triggers from thought, sight, smell, and taste of food, even when we are not hungry and do not need that food. We tend to overeat if food is appealing. Naltrexone is known to block chemically induced pleasure from alcohol. It stands to reason to try this medication by itself, in conjunction with a reduced calorie diet, increased physical activity, and other behavioral modification to achieve weight loss.
  4. Bupropion can be added separately to improve the rate of success. There is no reason to believe that only a fixed dose combination of Naltrexone and Bupropion is logical for all patients.

Naltrexone has certain advantages over other medications.

  1. Naltrexone does not increase heart rate and does not increase blood pressure so it is safe in most obese patients, hypertensive patients, patients who have breathing problems, patients who have increased risk of heart attack and stroke. These are patients who can not be prescribed Phentermine preparations.
  2. Naltrexone can be used for a longer period than Phentermine, which is restricted to three months of continuous use.
  3. Naltrexone has no interaction with diabetic medications. It does not increase blood sugar, it does not decrease blood sugar and is safe in diabetics.
  4. Naltrexone can be prescribed to patients who are taking SSRI or SNRI anti-depressants. These patients can not be prescribed Belviq.
  5. Naltrexone can be used even if you drink. Qsymia is not recommended to use with alcohol, and Naltrexone is 1/10th the cost of Qsymia.

I am prescribing Naltrexone for weight loss in selected patients who meet the current recommendations for treatment of obesity.

Obesity is defined as a Body Mass Index of 30 or more. To calculate it you need to know your weight and height.

CDC Online BMI calculator

Body mass index table

Generally accepted indication for treatment of obesity:

  1. Failure of diet and exercise regimen.
  2. BMI 30 or greater, or
  3. BMI 27 + Risk factors (high blood pressure, diabetes, lipid disorders, etc.)

Tip: Treatment of obesity is covered under most health insurance plans. Yo do not have to go to a weight-loss clinic.

Many medications require that you jump through hoops to get it through your insurance. Naltrexone is almost always covered, but you have to find a PCP who is familiar with Naltrexone and is willing to prescribe it. Because it is considered off label use, many providers are not willing to prescribe Naltrexone, … you may be able to get Contrave instead.

Treatment costs at my clinic: Naltrexone for weight loss

I am not a provider for any insurance. I can not assist you in filing claims or getting pre-authorizations.

Description Cost
Clinic visit Initial enrollment $275
Monthly visits $95 per month
Medication costs for 50mg tablet per day $1 to $2 per tablet = $30 to $60 per month. Mostly covered by insurance, prior authorization generally not required.
Lab tests To be done through your PCP. CHEM-7, CBC, Lipid Profile, Thyroid profile, etc., are all covered by your insurance and are part of yearly wellness visits done by your PCP.
Diets/Meals You can plan your own 1500 Cal diet or less, education and assistance is provided, free self help resources are available. There is no need to buy any branded meals or diets.
Exercise You can plan your own exercise regimen. Education and assistance provided, free self help resources are available. You can join fitness clubs or gyms and exercise in climate controlled comfort for $10 to $25/month.

Weight-loss medications and how they work

Belviq, Belviq XR (lorcaserin) has been withdrawn from the U.S. market because a safety clinical trial showed an increased occurrence of cancer.

If you have health insurance / prescription plan, then the following medications may be available to you. Discuss with your PCP. These medications generally require pre-authorization and require documented failure of diet and exercise alone. There is further rules about which medications will be covered first. If your PCP does not want to deal with it then you can request a referral to a weight-loss management provider, diet counselor / nutritionist etc. Be prepared to jump through a few hoops.

Medication – How it works Problems / Contraindication

Contrave (Naltrexone+Bupropion)
Naltrexone is an opiod receptor blocker. Bupropion is Nicotine receptor blocker and also increases Norepinephrine and Dopamine.
Works by reducing craving for food and causing early satiety, thus reducing the amount of food eaten.

Can not be prescribed to patients who are taking opioid medications for pain.

Suppresses appetite.
Schedule IV Controlled Substance
Can not be prescribed to patient who have high blood pressure, high heart rate, chest pain, or have had a heart attack.
Xenical, Alli (orlistat)
Reduces fat absorption from the intestine.
Available as OTC, no prescription required.
Gallstones, kidneystones, malabsorption syndrome, abdominal pain, diarrhea, flatulence, incontinence.
Long term use can cause malabsorption syndrome, nutritional deficiency. Patients may need to supplement with Fat soluble Vitamins A,D,E, and K.
Qsymia (Phentermine+Topiramate)
Phentermine is a sympathomimetic drug, suppresses appetite
Topiramate is an anti-seizure medication, suppresses appetite
Can not be prescribed to patients who have high blood pressure, and are at risk of heart attack or stroke. Prior authorization required, Restricted availability on insurance plans.

Cost comparisons of medications: Based on average costs displayed on GoodRx

Medication Cost per tablet Cost per month
Naltrexone 50mg tablet, 30 tablets $1 – $2 $30 – $60
Bupropion Generic 150mg tablet, 60 tablets $1 – $2 $30 – $60
Contrave 8mg Naltrexone/90mg Bupropion, 30 tablets $5 – $10 $150 – $300
Qysmia (Phentermine 7.5mg/Topiramate 46mg) capsule, 30 capsules $7 – $10 $210 – $300
Phentermine (Adipex-P) 37.5mg tablet, 30 tablets $0.5 – $1 $15 – $30
Phentermine (Lomaira) 8mg tablet, 90 tablets $0.5 – $1 $45 – $90
Xenical (Orlistat) 120mg capsules, 90 capsules $10 – $20 $300 – $600
Alli (Orlistat) 60mg capsules, 90 capsules, OTC $.50 – $1 $45 – $90


Tip: If you have health insurance coverage then obesity work-up, and all the above medications may be available to you through your Primary Care Provider. You do not have to go to any special weight loss clinic.

Basic lab tests for the evaluation of Obesity

Patients need the following lab test results before they are offered an appointment. These tests are considered to be routine tests for the evaluation and workup of any patient with obesity, are generally covered by insurance, and can be done through your PCP as a part of your annual wellness check.

Tip: Your PCP can order a general health panel, which is an annual benefit under many insurance plans. This covers CMP + TSH + CBC. Additional tests can be ordered as indicated.

  1. CMP(Comprehensive metabolic panel): Determines baseline liver and kidney function that will guide whether certain medications can or can not be prescribed. Includes BUN, Creatinine, Glucose, and serum elctrolytes.
  2. Hepatic panel + Renal panel or BMP, also called CHEM-7, SMA 7, as an alternative to above test.
  3. CBC (Complete blood count): Anemia is an indirect determination of nutritional status, and may preclude use of lipase inhibitors like Orlistat.
  4. Thyroid profile: Hypothyroidism as a cause of low metabolic rate and resultant obesity needs to be excluded or treated.
  5. Lipid profile: To determine baseline levels and monitor treatment progress.
  6. EKG: Required to determine if sympathomimetics like Phentermine can be prescribed.
  7. Testosterone for men: Low testosterone or high estradiol levels may contribute to obesity.
  8. Tests to exclude polycystic ovaries as a cause of obesity in women.

If a medical reason can be found that is causing or contributing to obesity then that must be treated first. Next step is diet and exercise to reduce weight. Only after these methods have been tried and have not achieved the desired results that one should look towards medications for weight loss.

Most anti-obesity programs recommend that medications should be discontinued if the patient has not achieved >5% weight loss by the end of 12 weeks. Probably because side effects increase if you take the medication for longer periods and in higher dose.

Naltrexone can be taken in a higher dose and for a longer period without significant side effects. When used for the treatment of alcohol addiction it has been used at 50 to 100mg/day for a periods longer than one year.

Useful links

NIH: Aim for a health weight

CDC: Defining Adult Overweight and Obesity

If diets and exercise have not achieved the desired results then adding a medication may help you achieve additional weight loss.

If Naltrexone can help you reduce your weight 5%, dieting another 5%, and exercise another 5% … that is a total of 15%. Naltrexone is my preferred medication, it is inexpensive, has low incidence of side effects, and can be taken for a longer duration.

This page was last modified on: April 25, 2020