Fat burners are supplements that claim to help you burn fat and lose weight. In my telehealth functional medicine clinic, I have seen many patients turn to fat burners as a way to lose weight and boost their metabolism.

While there’s certainly a lot to be skeptical about when it comes to big weight loss claims, some ingredients in these products are better than others. Some ingredients in weight loss supplements support gut health, boost your metabolism, and, as a side benefit, may support weight maintenance.

But high-quality supplements for weight management aren’t just marketed as “fat burners” on their own, because solid gut health isn’t as exciting as rapid weight loss claims. Are fat burners safe in the short term, though?

Read on to learn more about how they work, their side effects, and my preferred long-term weight loss solutions as a functional medicine provider.

How Do Fat Burners Work?

Fat burners are designed to help you lose weight by boosting your resting metabolic rate and energy expenditure, blocking fat storage in your body, and suppressing your appetite. Some contain naturally occurring ingredients, while others include compounds made in a lab.

Some ingredients in these supplements may help your body do some of the things they promise, but their effectiveness can vary dramatically. Your overall health, diet, and level of physical activity matter, as do the combination of ingredients inside every bottle.

How long they stay in your system varies by ingredient. When you’re looking at a long list of ingredients on a supplement label, it can be hard to tell whether what you’re taking will do more harm than good.

How To Know If A Weight Loss Supplement Is Safe

Supplements are already challenging to navigate, but the fat burner market can be particularly overwhelming because of aggressive marketing tactics by some brands. Since no supplement goes through approval processes by the Food and Drug Administration (FDA), you need to do your own research about the efficacy of a product on the shelf.

Start with the ingredients. You’ll want to know what each ingredient does and whether there are any potential side effects. From there, look for supplements manufactured by reputable companies that use good manufacturing practices and third-party testing.

If you find a weight loss supplement you want to try, talk with your healthcare provider first, especially if you have any underlying health conditions or are taking medications. There may be side effects or contraindications to consider that make existing medications less effective.

Ingredients To Look For

Some common ingredients appear in popular fat-burning supplements, and they’re not all bad if taken in moderation. The problem is that it can be hard to know the dosage of each when they’re combined with other, less desirable ingredients.

The ingredients below all have evidence behind them as supporting some aspect of weight management, but it’s always best to take them in their natural form. I’ll share tips on how to boost your intake of natural fat burners for healthy and sustainable weight loss.

Note: My list isn’t comprehensive. If your fat-burning supplement contains ingredients not listed below, I highly recommend researching ingredients for yourself (including the effective dosage) and discussing supplements with a functional medicine provider.

Caffeine

Caffeine is one of the most common stimulants in fat burners for the same reasons it perks you up in the morning. It stimulates your nervous system, which may help you burn more calories.

Caffeine comes with quite a few additional benefits. It supports healthier aging and may improve your mood. It’s linked to a lower cancer risk and a reduced risk of developing diabetes. (1, 2)

Here’s the caveat for those positive health effects: You need to be able to metabolize caffeine efficiently. For slow caffeine metabolizers, too much caffeine can increase heart disease risk, trigger gut issues, and spike cortisol levels. None of that is good for weight loss or overall wellness.

Consuming a lot of caffeine is also risky for certain folks with a history of anxiety or other mental health disorders or for growing bodies. No, it doesn’t actually stunt growth, but I recommend waiting to try much caffeine until your early twenties, if possible.

The key is to limit caffeine to safe levels. The FDA says 400 mg/day is OK for most adults. If you’re sensitive to it, under 18, or diagnosed with conditions exacerbated by caffeine, like anxiety, insomnia, rapid heart rate, or acid reflux, you should be even more cautious.

LISTEN: Is Coffee Harmful or Healthy, Inflammation Insights, Sleep Tips + How Toxic Relationships Show Up On Labs | Dr. Will Cole & the Functional Medicine Team

Green Tea Extract

Green tea contains caffeine, a known metabolism booster, but it also contains antioxidants known as catechins. These polyphenols play a role in both a healthy metabolism and thermogenesis, the process where your body burns fat for energy, on top of added cardioprotective effects. (3, 4)

In one study of women struggling with central obesity, high doses of green tea extract resulted in significant weight loss, reduced belly fat, and lower cholesterol. (5) Keep in mind here that green tea comes with similar precautions as what I described with caffeine above.

Soluble Fiber

Soluble fiber can help you feel more satiated by regulating hunger hormones like ghrelin and slowing the movement of food through your gut. (6) It also acts as a natural prebiotic for a healthier gut microbiome, which may positively impact your metabolism and energy regulation.

This one is easy to add to a gut-friendly diet without relying on fat burners. Beans, nuts, seeds, barley, and fruits and vegetables like broccoli, peas, and apples are rich in soluble fiber. Just watch your intake — too much can cause bloating and constipation.

Carnitine

Carnitine is a naturally occurring compound that plays a role in energy production. Some research suggests it may increase fat metabolism, boost muscle mass, and reduce fatigue when you’re exercising, potentially improving the efficiency of your workouts and calorie burning. (7, 8)

Side effects are rare, but high doses in supplement form as L-carnitine have been linked to gastrointestinal distress. You can get natural, more bioavailable sources of carnitine in many meat and dairy products, like beef, chicken, milk, and hard cheese.

Capsaicin

Capsaicin, the compound responsible for the spicy heat in chili peppers, has shown promise in increasing metabolism. (9) That heat you feel eating spicy foods is the same premise behind supplements that include this ingredient. The compound generates heat in the body, which may enhance fat burning.

Some research suggests it might make you less hungry, which is why it’s often used in appetite suppressants. (10)

Spicy peppers like jalapeno and habanero, pantry spices like cayenne, and salsas all have the same effect — consuming capsaicin like this means you don’t have to worry about additives in fat burners. If your body doesn’t tolerate spice or you have GI issues exacerbated by the heat, skip this one in favor of milder alternatives.

Conjugated Linoleic Acid (CLA)

CLA is a fatty acid found in meat and dairy. It may have modest effects on weight loss by affecting enzymes involved in fat metabolism. (11) For natural sources, try grass-fed beef and butter from grass-eating cows. Eat those foods in moderation to prevent a rise in cholesterol.

Avoid These Ingredients

Any supplement, whether it’s weight loss pills or a nutritional aid, can become harmful if you take too much of it. The common fat burner ingredients below come with more red flags than they’re worth, especially if the wins are only short-term.

Yohimbe

Yohimbine, the active ingredient from the bark of the Pausinystalia yohimbe tree, has been used as an aphrodisiac to treat erectile dysfunction as well as for its fat-burning potential. Early studies saw potential in how it regulated adrenaline, or epinephrine, to target stored fat cells.

Research since has shown mixed results, and that taking too much yohimbe can have dangerous side effects. (12) Reported side effects have included anxiety, rapid heartbeat, high blood pressure, and nausea. A few have reported seizures, kidney damage, and heart attacks. (13)

There have also been cases where dosages on supplements haven’t matched what’s inside, causing users to consume much more than recommended. It’s troubling enough that countries around the world have started regulating it more aggressively, so it’s best to avoid for now in terms of weight loss.

If you choose to take yohimbe for erectile dysfunction, make sure to keep a close eye on any symptoms that arise and take it under the supervision of a healthcare provider.

Usnic Acid

Usnic acid is a compound found in lichens known for its antibacterial properties. When taken orally, supplement brands claim it can increase metabolism and fat oxidation.

Research on this is mixed, but studies on its adverse effects are numerous. (14) Usnic acid has been linked to gastrointestinal problems, allergic reactions, and liver damage and failure. (15)

You won’t likely find this one on drugstore shelves, but it’s still in weight loss supplements sold in online marketplaces.

Bitter Orange

Bitter orange, also known as Citrus aurantium, is a common weight loss supplement ingredient, but whether or not it can actually support weight management is unclear.

A systematic review of human studies found that bitter orange may increase blood pressure and heart rate when taken over the long term. (16)

These Ingredients Probably Aren’t Dangerous OR Effective

When it comes to fat burner ingredients, there are several that have no notable negative effects when taken at safe doses, but are thought to have very little impact on weight. These probably won’t hurt you, but they might waste your money:

• Beta-glucans
• Chromium (this one may cause disruptive side effects)
• Coleus forshkohlii
• Garcinia cambogia
• Guar gum (this has gut-related benefits but isn’t necessarily effective for weight loss)
• Hoodia (it doesn’t cause many serious side effects, but doesn’t help patients lose weight and causes many uncomfortable symptoms) (17)

Is It Working?

A fat burner is effective when you see the results it claims. You’ll want to monitor any changes in body composition, like your body fat percentage or waist circumference beyond just your body weight. Track changes in your energy levels, especially during workouts, and appetite changes.

Pay attention to any negative side effects, too. Fat burners, even those considered safe fat burners, are meant for short-term use. Results are promised in as little as 4-6 weeks, but some users stay on these supplements for months. This isn’t smart weight loss for most of us.

Sustainable, long-term weight loss is a more individualized approach that takes underlying obstacles to weight management into account. Ultimately, your doctor or a functional medicine practitioner are your best resource for getting to the root of your issues.

5 Safe, Sustainable Weight Loss Methods To Try

There is no quick fix when it comes to weight loss. Ultimately, we have to get healthy to lose weight. At my clinic, I work with my patients to get to the root of barriers to long-term weight loss. There may be a hormone imbalance or gut problems at play that fat burners won’t fix.

Once we heal whatever dysfunction is going on underneath the surface, long-term weight management can follow. The tools below are the first I look to when working with patients struggling with their weight.

1. Eat More Healthy Fats

Healthy fats are important to balanced blood sugar, which can support weight loss. Your body uses glucose from sugar and carbs for energy, but once those easy-access stores are depleted, your body will start burning fat.

The best healthy fats are medium-chain triglycerides like the ones found in coconut oil. These are the most readily available for your body to use as energy.

2. Try Intermittent Fasting

Intermittent fasting, where you limit your food intake for pre-determined stretches of time, is linked to reduced inflammation and decreased insulin resistance. Both can help prevent diabetes and encourage weight and fat loss.

The goal of fasting isn’t about fewer calories. I practice fasting in my daily life. If you want to learn more, check out Intuitive Fasting, my book on embracing healthier eating patterns and the benefits of the practice.

3. Get Your Hormones Checked

Leptin is a hormone produced in fat cells. Its job is to tell your brain to burn fat for energy. Leptin resistance occurs when your body stops recognizing this hormone and tricks your metabolism into thinking it’s starving, causing it to continually store fat instead of burning it off.

A blood test can easily check your leptin levels. Your ideal range should be between 4 and 6 ng/dL.

4. Heal Your Gut

An unfavorable balance of gut bacteria can lead to a slowed metabolism, which can affect how your body burns calories and stores fat. Balance your microbiome by identifying food triggers, eating gut-healthy foods, and finding the root of your GI symptoms.

5. Try Supplements

I’m not talking about fat burners here. Natural supplements like berberine that target nutritional deficiencies or health conditions affecting your metabolic function can be a positive addition to your weight loss plan. Talk to your healthcare provider about supplements that could help your case.

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