While you might only think of pre-workout supplements as caffeine that gives you the boost you need to train hard, many pre-workout formulas include so much more. For instance, if you’re laser-focused on getting shredded, you can opt for a thermogenic pre-workout.

So what are thermogenic pre-workouts all about and should you add one to your training routine? Consider this expert advice—and prepare to bring the heat.

Hold On, What Does “Thermogenic” Actually Mean?

Important background information here: Supplements identified as thermogenic “may promote the biological process known as thermogenesis, which is the production of heat energy in the body,” explains nutritionist Brian Tanzer, M.S., Manager of Scientific Affairs for The Vitamin Shoppe. And what is heat energy, exactly? Calories.

Basically, the idea is that by producing heat in our bodies, thermogenics increase the amount of calories we burn (a.k.a. our metabolism), adds Dr. Jacob Wilson, Ph.D., C.S.C.S.*D, CEO of The Applied Science & Performance Institute and member of The Vitamin Shoppe Wellness Council.

What To Know About Thermogenic Pre-Workouts

Since thermogenics are all about boosting metabolism and burning calories, thermogenic pre-workouts are formulated to support our ability to burn fat, making them a go-to for people whose primary fitness goal is to shed body fat, Wilson explains.

Read More: How To Eat And Train To Boost Your Metabolism

How exactly do they accomplish this, though? Also known as “stimulant” or “high-stim” pre-workouts, thermogenic pre-workouts “typically contain high amounts of caffeine along with other ingredients that may provide a “kick” to your nervous system,” says Tanzer. This extra boost comes in the form of ingredients like yohimbe, a tree bark extract known to boost thermogenesis. You may also find other known metabolism-boosters, such as green tea extract, hot pepper extracts, or l-carnitine (which supports the body’s ability to turn fat into energy). Of course, caffeine itself is also famous for supporting your metabolism and fat-burning.

Who Should (And Should Not) Try Thermogenic Pre-Workouts?

Given that, if you’re looking to rev your metabolism or tweak your usual supplementation routine to support your fat-loss goals, a thermogenic pre-workout supplement might be just what you need. “They are typically formulated for the avid gym-goer who trains hard and is looking for that extra boost,” Tanzer says. So, if you’re no stranger to caffeine-containing workout supps, a thermogenic might be just the level-up you’re looking for.

That said, because these supplements are highly stimulating, they may not be an ideal option for people who are sensitive to caffeine or other stimulants. Wilson also doesn’t recommend them for hard-gainers or anyone trying to put on mass.

Read More: 5 Signs You Need A Break From Caffeine

Plus, since many of these pre-workouts contain high amounts of caffeine and other ingredients that increase heart rate and blood pressure, Tanzer recommends anyone with medical conditions or who takes prescription medications check with their doctor before updating their supplement routine.

Popular Pre-Workout Picks

Not sure where to start with a thermogenic pre? These picks are super-popular amongst The Vitamin Shoppe customers.

1. Evolution Nutrition Blue Raz ENGN SHRED Pre-Workout, which contains 260 milligrams of natural energizers like coffee bean extract, plus yohimbe, red pepper fruit extract, l-carnitine, and so much more for a hardcore burn.
2. GAT Sport Pink Lemonade Nitraflex Burn, an amped-up version of GAT’s popular Nitraflex pre-workout that contains 325 milligrams of caffeine and l-carnitine, green tea extract, cayenne pepper fruit extract, and cassia bark powder, among others.
3. Betancourt Nutrition Tropical Paradise B-NOX Ripped, a thermogenic pre from the long-respected sports supps brand that’s packed with a number of proprietary blends for energy and endurance.
4. Cellucor Midnight Cherry C4 Ultimate Shred, the brand’s most explosive version of C4, a supp that offers high amounts of caffeine, beta-alanine, citrulline, and more—including the brand’s proprietary C4 Ultimate Shred & Thermogenic Matrix.

The Do’s And Don’ts Of Taking Thermogenic Pre-Workouts

Should you decide to give a thermogenic pre-workout supplement a try, there are some important best practices (and mistakes to avoid) worth keeping in mind.

The Do’s

When starting out with a high-stim pre-workout, Tanzer suggests testing your tolerance by taking just half—or even a quarter—of the recommended amount. From there, you can increase how much you take—up to the full recommended amount—in order to find the amount that feels best for you.

Wilson also recommends waiting to incorporate thermogenic pre-workouts until after you’ve hit a fat-loss plateau, since that’s when the boost they provide will be the most helpful. He also suggests cycling your supplements and taking a thermogenic pre-workout two or three times per week, preferably when doing circuit training, cardio, or higher-rep training that’s already boosting your heart rate and stimulating your nervous system. Continue this cycle for four to six weeks, then take two weeks off your high-stim pre-workouts completely before repeating. Taking this approach minimizes your tolerance for (and dependence on) these supplements.

The Don’ts

Perhaps the biggest thing to avoid? “Do NOT exceed the recommended dosage,” Tanzer urges. Since the ingredients in thermogenic pre-workouts are so stimulating to your nervous system, going overboard can do more harm than good. This is exactly why Wilson recommends taking a supp-cycling approach; doing so helps you avoid building up a tolerance or dependence that leads you to take too much or exhaust your nervous system (which inevitably leads to fatigue and lethargy).

Another important (and perhaps obvious) mistake to avoid? “Do not take [thermogenic pre-workouts] at night, as you won’t be able to sleep!” Wilson emphasizes.

Read More: I Drank A Gram Of Caffeine a Day—Here’s What Happened When I Quit Cold Turkey

Finally, Tanzer also recommends avoiding the temptation to participate in the recent social media trend of “dry scooping,” which involves tossing back an entire scoop of dry pre-workout powder. “This causes choking and/or severe irritation to the throat and esophagus,” he says. “In some cases, the choking can cause the product to get into the lungs, which may cause harm.”

The Bottom Line

Ultimately, the most important thing to remember about thermogenic pre-workouts is that they are simply one tool to incorporate in your get-shredded plan.

There is a multitude of other strategies to focus on if fat loss is your top priority, Wilson says. From cycling calories, to adjusting your carbohydrate intake, to doing high-intensity interval training, to getting at least 12,000 steps in, fat loss requires holistic lifestyle change—and simply swapping your pre-workout supplement can’t make up for that!