Does Naltrexone Help With Weight Loss?

It seems as if new weight loss trends pop up every day. From diets like carnivore to keto, medications like Ozempic and now naltrexone, it's difficult to know what works and what is just the latest diet craze. Sure, a pill to help shed the pounds sounds great, but is it too good to be true? Most medications come with a paragraph of warnings, usually printed in the smallest font possible — obscuring the long list of side effects and risks. To make matters more complicated, weight loss doesn’t always mean better health. If we’re looking for a long-term solution to a healthier lifestyle, we need a clearer look at the whole picture.

Whether you’ve been prescribed naltrexone and are wondering why the number on the scale is going down, or you’re looking for a medication to aid in weight loss, understanding the science behind how naltrexone works can provide some answers. So, let’s investigate what naltrexone is, how it works, and who stands to benefit most from using it.

What Is Naltrexone?

Naltrexone is approved by the U.S. Food and Drug Administration (FDA) and used to treat alcohol use disorder (AUD) and opioid use disorder (OUD). It’s a highly controlled substance that requires a prescription and, often, administration by a licensed practitioner. It’s used in medication-assisted treatment (MAT) as just one component of a comprehensive treatment plan.

Naltrexone comes in a pill and extended-release intramuscular injection form. Both forms are used to supplement a combination of behavioral therapies and counseling for a holistic approach to treating substance use disorders.

Uses for Naltrexone

These are two common implementations of naltrexone aside from treating substance misuse: 

• Low-dose naltrexone (LDN). Off-label naltrexone has been shown to have anti-inflammatory effects and has been trialed for a number of different uses. LDN ranges from a 1-5 mg daily dose, which is about one tenth of the strength of clinical naltrexone. While more research is necessary, LDN has shown moderate success improving symptoms of multiple sclerosis, long COVID, fibromyalgia, cancer, autoimmune conditions, and more.
• Contrave. This FDA-approved medication used to treat obesity is a combination of naltrexone and bupropion. Bupropion is a norepinephrine/dopamine-reuptake inhibitor commonly used as an antidepressant. The combination of naltrexone and bupropion influences the brain’s reward system, which can impact eating behaviors. Contrave is found to be most effective when combined with lifestyle changes such as exercise and diet.

Naltrexone is used to treat opioid misuse, alcohol misuse, inflammatory conditions, obesity … this pharmaceutical multitool has quite the skillset. So just how does it do all this?

How Does Naltrexone Work?

Naltrexone is classified as an opioid antagonist or opioid blocker. As the name suggests, drugs like naltrexone prevent substances from binding to opioid receptors, effectively blocking the pleasure response from substance use. 

Since naltrexone blocks a substance's ability to give us those familiar positive feelings, we quickly become less psychologically dependent on it — we crave it less, and it doesn’t seem quite so appealing. Ever had a moment when you opened a bag of chips and couldn’t stop until the bag was empty? Now imagine if you suddenly lost your sense of taste while eating the bag of chips. Sure, you’d probably freak out because you’d lost your sense of taste, but most of us would also stop eating the chips since taste is the reward that keeps us going back for more.

The physiological effects of drinking stem from dopamine release and activation of the hypothalamus-pituitary-adrenocortical (HPA) axis. Research shows that naltrexone diminishes dopamine release and HPA activation, adding to its effectiveness as a treatment for substance dependence. Naltrexone works as a medication to decrease alcohol opioid misuse, but let’s take a look at why it’s also tied to weight loss. 

The Naltrexone-Weight Loss Connection

Naltrexone blocks opioid receptors, which reduces intoxication effects, but its impact on our reward system also causes secondary effects that can influence our weight. The opioid system regulates our mood, hunger, pain, and reward system. Naltrexone's damper on the opioid system can lead to a number of side effects.

• Decreased appetite. Lower hunger levels result in reduced caloric intake.
• Reduced reward feedback. This aids in decreasing overall food intake, as the reward signals we get from food are reduced.
• Improved insulin sensitivity. Proper blood sugar regulation is tied to better weight management and lower risk of diabetes.
• Increased energy. We may be more inclined to participate in physical activity, helping to burn more calories. High energy also suggests that our body systems are functioning at optimal levels.
• Improved mood. This helps to decrease our stress hormone levels, which can make weight loss easier.

Alcohol and Weight

In contrast to naltrexone, alcohol is linked to weight gain. Here are four main ways that alcohol causes weight gain:

• Extra calories. Alcohol contains calories that can add up quickly. For example, a pint of beer is around 200 calories. Downing two pints is equivalent in calories to eating a cheeseburger. However, alcohol is composed of empty calories, meaning there is little to no nutritional value. The overall increase in caloric intake explains why alcohol is frequently linked to weight gain.
• Lowered inhibitions. Drinking alcohol lowers our inhibitions, giving us the feeling of “letting loose.” This is tied to making unhealthier food choices (drunchies, anyone?). There’s a reason we don’t usually gravitate towards grazing on raw carrots over a basket of fries while out drinking.
• Altered fat processing. Our body prioritizes metabolizing alcohol, which causes short-term impacts on our fat-burning processes. Damage to the liver can also alter the way our body metabolizes carbohydrates and fats in the long run.
• Effects on hormones. Alcohol impacts hormones in our brain that sense hunger and fullness. It stimulates our hunger hormone — increasing our appetite. Alcohol also inhibits our fullness cues, which can lead to overeating. 

Weight Loss Intention

It is important to make the distinction between the different ways that naltrexone is used for weight loss. Understanding the intention for the use of naltrexone helps us examine its practicality as a weight loss solution. We can define the different intentions this way:

• Primary use. This refers to using naltrexone as a weight loss medication rather than a treatment for AUD or OUD. Some compounded forms of naltrexone are FDA-approved to treat obesity.
• Secondary use. This weight loss intent is based on utilizing the side effects of naltrexone and capitalizing on its appetite-suppressing effects rather than using the medication as intended. This can be compared to misusing Pepcid to reduce alcohol flush symptoms rather than its primary purpose as a treatment for heartburn.

Now that we have a better understanding of how naltrexone and weight loss are connected, let’s take a look at the versatility of naltrexone to see how it can treat various conditions.

Drinking on Naltrexone

Naltrexone is an approved treatment for alcohol use disorder but is being explored for other treatments, which brings up the question of drinking while taking naltrexone. 

The opioid-blocking effects of naltrexone inhibit the feelings of intoxication but do not prevent the other impacts of alcohol. While drinking on naltrexone, we continue to experience impairments such as delayed response time, lack of motor coordination, and impaired thinking. It’s important to note that driving and participating in other activities that require full coordination and function should not be attempted. 

While used to reduce alcohol dependence, starting naltrexone does not require full abstinence from alcohol. The Sinclair Method actually uses naltrexone in conjunction with drinking to slowly reduce the desire for alcohol consumption. Naltrexone should always be used as part of a treatment program that involves behavioral treatment and therapies in order to help reduce dependence. Individual needs will vary, and it’s important to discuss personal circumstances with our own practitioner and treatment team.

Dangers of Using Naltrexone for Weight Loss

Before taking a look at some of the common side effects of naltrexone, it’s important to note that naltrexone should not be taken with any opioids (including opioid-containing medication). Before starting naltrexone, a detox period of up to two weeks may be needed to help prevent overdose or withdrawal symptoms. Used as prescribed, naltrexone is relatively safe but may cause side effects such as:

• Nausea
• Constipation
• Diarrhea 
• Fatigue 
• Headache 
• Insomnia 
• Anxiety 

More serious side effects include depression, allergic reactions, and pneumonia. 

Contrave, the FDA-approved medication for obesity, also contains bupropion, adding to the list of naltrexone side effects for weight loss. Common side effects of bupropion are:

• Dizziness
• Dry mouth 
• Stomach pain
• Sleep disruptions
• Tremors
• Agitation 

Bupropion is an antidepressant and requires warnings for depression, mood changes, and increased risk for suicidal thoughts. If we are susceptible to mood changes, we should stay in regular contact with our prescribing physician and check in regularly with the professionals helping guide our treatment regimen.

Now that we're aware of the potential risks of using naltrexone for weight loss, let’s take a look at who may benefit from it. 

Who Should Take Naltrexone for Weight Loss?

If used as a medication for weight loss, specific criteria should be met prior to taking naltrexone. Naltrexone should be used only as a last resort because it comes with more risks than many other methods of weight loss. If excess weight is causing medical concerns and we haven’t been able to lose weight through traditional methods, we could benefit from using naltrexone. 

Those of us who are prescribed naltrexone for other purposes should not make weight loss an intention or priority. It can be beneficial to implement healthy habits that, coupled with naltrexone’s weight-reducing effects, can lead to an overall healthier lifestyle. While naltrexone can be instrumental in weight loss, it's not appropriate for everyone to use. 

Who Should Not Take Naltrexone?

Naltrexone is effective for a number of different conditions but can cause adverse effects when not used appropriately. It should not be used by anyone who is ...

• Under 18 years of age. Naltrexone is FDA-approved for adults 18 and older. Its effects are still being studied for adolescents, and naltrexone is not recommended as a treatment method at this time. 
• Still using opioids. This includes opioid-containing analgesics and illegal substances. Using naltrexone while taking opioids can lead to overdose and serious withdrawal symptoms. Before starting naltrexone, an opioid detox period is needed, and a naloxone test may be administered to prevent the risk of overdose. 
• Experiencing opioid withdrawal. Taking naltrexone while experiencing active opioid withdrawal exacerbates symptoms that can lead to the need for medical attention. 

Now that we’ve analyzed who should and shouldn’t use naltrexone, let’s explore some actions we can all take to better our overall health.

Tips for Living a Healthy Life

Health and wellness can be subjective, but implementing healthy habits can improve our physical and mental well-being. These are some ways we can positively influence our health:

1. Stay active. Exercise is not only great for our physical health but also improves our mood and mental health. While we commonly think of exercise as running on the treadmill or lifting weights in the gym, movement can look different for everyone. Gentle stretching or walking outside are other ways to stay active that are still beneficial to our health. 
2. Eat a healthy diet. Again, “healthy” is subjective, but generally speaking, a not-overly restrictive diet focused on whole foods and a balance of protein, carbohydrates, and fats helps with the proper functioning of the systems in our body. Avoiding toxic substances like alcohol and tobacco is also part of maintaining a healthy diet.
3. Connect with others. We don’t have to be social butterflies, but building connections has positive impacts on our mood, self-esteem, and overall contentment. 
4. Pursuing interests. Engaging in activities that we are passionate about helps us live a happier and more fulfilling life. 

Whittling Down

Naltrexone seems to be a jack of all trades. It’s an effective treatment for alcohol and opioid use disorder and can contribute to weight loss, whether primary or after-effect. As with any drug, there is a long list of potential risks. Using naltrexone for weight loss requires thorough consideration and should be used only after other alternatives have been explored. Body weight is but a small fragment of our overall health. We can manipulate plenty of other aspects of our well-being to live a happy and healthy life. Like the great Roman poet Virgil said, “The greatest wealth is health”.