Thermogenics: What Are They? Do They Work For Weight Loss In 2025?

Weight loss supplements are very popular among individuals seeking additional support for reaching their goals. Thermogenics are often marketed as fat burners or a solution to help with energy levels, giving you that extra boost to get through your workouts. As they have potential side effects, it is important to be aware of how they work and how best to use them.

Many thermogenic supplements are included in weight loss supplements, and it is helpful to identify them in a list to predict their effects. So, which supplements are considered a thermogenic supplement? How do thermogenics work, and how can you ensure they are used safely? 

We will examine several more commonly used thermogenic dietary supplements in closer detail. 

What Are Thermogenics?

The term thermogenic can be broken down into two basic parts: “thermo” (heat) and
“genic” (produce). Essentially, thermogenics produce heat. Within the body, this term refers to a supplement’s ability to boost metabolism. At times, these are referred to as fat-burning pills.

The goal of these supplements is ultimately to contribute to weight loss as the body burns calories. Ideally, much of this activity will contribute to fat loss through increased fat metabolism. When these supplements are evaluated for efficacy, body weight and body composition changes are tracked.

Some of the more common thermogenic supplements include:

• Caffeine: A naturally occurring stimulant most often associated with coffee, although it is found in many different plants. Sources include guarana, yerba mate, and certain teas, all commonly listed ingredients in combination supplements.
• Green tea extract: An herbal supplement containing caffeine and active catechins. The primary active catechin is epigallocatechin gallate or EGCG. This specific catechin is often featured on ingredient labels.
• Garcinia cambogia: A natural hydroxycitric acid (HCA) source derived from fruit rinds. HCA^[1] may slow down fatty acid, cholesterol, and triglyceride production.
• Capsaicin: The naturally occurring substance that makes spicy peppers spicy.

So, what does the research say about these supplements? 

Do Thermogenics Work?

Caffeine

Many thermogenic supplements contain caffeine, sometimes listed directly and other times associated with other ingredients. Caffeine has been evaluated more specifically as a pre-workout supplement. There is evidence^[2] that caffeine improves fat oxidation rates during exercise, but there is variability between individuals.

Considering the dosage of caffeine associated with a reliably significant effect on fat loss is important. It appears^[2] that a dose of at least 3.0 mg/kg, or about 1.36 mg per pound, is needed to produce a significant change in fat metabolism.

Green Tea Extract

Green tea is often listed in thermogenic supplements along with its primary catechin, EGCG, and it is important to remember that it is naturally caffeinated. Green tea supplements have been associated with improved fat metabolism. A green tea supplement,^[3] combined with exercise,  resulted in a significantly greater reduction in body mass index, body fat percentage, and waist circumference than exercise alone.

Garcinia Cambogia

Supplements containing garcinia cambogia have been highly touted over time and more thoroughly examined recently. The effects of garcinia cambogia on weight loss have been mixed,^[4] with many studies showing no impact compared with placebo. When combined with diet and exercise, there is a potential for benefit, but discussing the risks and benefits with your doctor is important before using the supplement.

Capsaicin

The effects of capsaicin supplements have been studied many times over the years, with some evidence of appetite suppression and increased fat metabolism. A recent review of the effects of capsaicin showed^[5] an overall decrease in BMI and body weight. However, these effects were fairly modest, highlighting the importance of diet and exercise for producing more significant results.

Natural Thermogenics

If you would rather avoid using a supplement, you can obtain a thermogenic effect naturally through your diet. If weight loss and a reduction of body fat are your objectives, a primary strategy is to create a caloric deficit. When you eat fewer calories than you burn, it will support weight loss.

If you are using caloric restrictions, it is important to maintain a healthy, balanced diet that continues to provide essential nutrients. Consider tracking your intake of proteins, carbs, and fats. The quality of your food matters, and the following choices can be helpful:

• Limit processed foods. These are high in sugars and saturated fats.
• Choose complex carbohydrates like whole grains.
• Choose healthier fats. Foods like salmon and avocados have a higher portion of unsaturated fatty acids.

Some ingredients in thermogenic supplements can also be implemented into your diet through a list of foods and beverages. For instance, you could drink green tea or coffee without adding cream or sugar. Peppers contain capsaicin, and the spicier the pepper, the higher the capsaicin content.

Combining a caloric deficit with exercise can be particularly helpful. Incorporating cardio training can help you reduce^[6] body fat and make it easier to maintain a caloric deficit.

Thermogenic Supplements

When thermogenics are provided in dietary supplements, these are often included among an array of other ingredients ranging from antioxidants to probiotics. Awareness of what they are and how they work can help you determine the best way to use the supplement safely and effectively. When choosing the best thermogenics, some important factors must be considered.

Among the over-the-counter products marketed for weight loss and muscle building, there are  many supplements that contain ingredients not listed on the label.^[7] Some of these ingredients have the potential to cause harm. Because of this, it is important to be aware of some indicators of quality that can help you choose a safe, reliable product.

• Good manufacturing practices, or GMP certification, refer directly to the manufacturing facilities. The FDA does not evaluate final over-the-counter formulations but provides standards for the facilities related to ingredients, storage, equipment, and staff. The FDA issues warning letters when manufacturers fail to meet these standards.
• Independent third-party testing helps confirm the ingredients in the product match the ingredients on the label, both in chemical identity and quantity. This also detects any potential contaminants. Third-party testing is a sign a product is more likely to be safe and reliable.

Choosing supplements with these characteristics can help you avoid getting blindsided by a potentially unsafe product. It is still important to consult your doctor before starting supplements to ensure the active ingredients are safe and effective for your needs.

Benefits & Drawbacks Of Thermogenics

Weight Loss Benefits

Taking active steps to promote weight loss can have numerous benefits. If you use thermogenics for weight loss, you are more likely to achieve it when combining consistent adherence to a healthy diet and exercise routine. Among individuals considered overweight, losing 5%–10%^[8] of baseline body weight is associated with:

• An improved self-image and quality of life.
• A lower risk of cardiovascular disease.
• Improved blood sugar control, reduced insulin resistance, and a lower risk of developing diabetes.
• Reduced knee pain and improvements in mobility.
• A lower risk of developing sleep apnea.

For those not considered overweight, taking steps to maintain a healthy weight will likely help you avoid these potential health concerns. Maintaining a healthy balance is crucial, especially if you are considering supplementation, dietary changes, or intense workout regimens. Checking in with your doctor and a registered dietitian can help ensure you are taking care of all your needs.

Side Effects & Precautions For Thermogenics

Caffeine

Caffeine plays a central role in many products marketed as fat-burning supplements. If you have other sources of caffeine in your diet or supplement regimen, it can be helpful to be aware of how these may add up. As total doses of caffeine increase, so does the potential for feeling jittery or having trouble falling asleep.

Some examples of supplements that contain caffeine^[9] are:

• Guarana.
• Kola nut.
• Yerba maté.
• Green tea.

The amount of caffeine likely to cause side effects can vary between individuals. In general, higher levels of caffeine have been associated with increased anxiety symptoms.^[10] There are still a lot of opportunities to assess the safety^[11] and the long-term effects of using caffeine despite a significant amount of existing research.

Many people associate caffeine with increases in blood pressure. While caffeine increases blood pressure, it appears this may be temporary and reversible as the body processes caffeine. In a recent review of multiple studies with long-term follow-up, there was no increased risk^[12] of developing hypertension or sustained elevated readings.

There have also not been any established links between caffeine and cardiovascular disease.^[13] However,  individuals with existing hypertension may be more susceptible to changes in blood pressure. Paying attention to your body and discussing supplements with your doctor can help ensure the overall effects remain positive.

Green Tea Extract

Keeping an eye on dosages is important in general, and you should not take more than the recommended amount of any supplement. This is the case for green tea extract, as doses of more than 800 mg daily of EGCG have been associated with liver toxicity.^[14]

Garcinia Cambogia

Many studies have highlighted garcinia cambogia as safe. The risks associated^[4] with garcinia cambogia include liver toxicity, serotonin toxicity, and potential induction of mania. If you have reduced liver function or are taking medications for mental health, it may be helpful to use garcinia cambogia cautiously.

Conclusion

Thermogenics are meant to boost energy and metabolism and are often marketed as fat-burning supplements. Caffeine is a commonly used thermogenic, and several other ingredients are often used for this purpose, including green tea extract, garcinia cambogia, and capsaicin. These supplements are often combined with other ingredients in some products.

It is helpful to be aware of these supplements and their effects to help ensure they are used safely and effectively. These are often recommended before workouts and are generally best taken in the morning due to stimulant effects. Maintaining a healthy balance is crucial, and consulting your doctor before starting a supplement can help ensure your overall well-being is kept top of mind.