Celsius can give your metabolism a temporary boost, but the effect is too small to drive meaningful weight loss on its own. A pilot study published in the Journal of the International Society of Sports Nutrition found that drinking a single can of Celsius increased metabolic rate by about 12 to 14% for two hours, tapering to around 8.5% by the third hour. That sounds impressive as a percentage, but in absolute terms it translates to burning maybe 70 to 100 extra calories over those three hours, roughly the equivalent of a small banana.
What Celsius Actually Does in Your Body
Celsius markets itself as a “fitness drink” that triggers thermogenesis, which is your body’s process of generating heat and burning calories. The main driver behind this effect is caffeine. A standard 12-ounce can contains 200 mg of caffeine, about the same as two cups of coffee. The Essentials line bumps that up to 270 mg per can. Caffeine stimulates your central nervous system, raises your heart rate slightly, and temporarily increases the rate at which your body burns energy at rest.
The drink also contains green tea extract, ginger, and guarana (another plant-based caffeine source), all of which have mild thermogenic properties. But caffeine is doing the heavy lifting. If you already drink coffee or tea regularly, you’re already getting much of the same metabolic bump that Celsius provides. Your body also builds tolerance to caffeine over time, which means the thermogenic effect shrinks with daily use.
How Much Extra Fat Does It Burn?
The company-funded pilot study measured metabolic rate increases after a single can. Participants saw a 13.8% rise at one hour and 14.4% at two hours, dropping to 8.5% at three hours. The researchers noted this was greater than the effect from Diet Coke, which contains about 46 mg of caffeine per 12 ounces compared to Celsius’s 200 mg. More caffeine, more thermogenesis. No real surprise there.
Here’s the math that matters: to lose one pound of body fat, you need a deficit of roughly 3,500 calories. If a can of Celsius helps you burn an extra 80 calories, you’d need to drink it daily for about 44 days to lose a single pound, assuming everything else in your diet stays exactly the same. That’s a painfully slow return, and it assumes you never develop caffeine tolerance. In practice, the effect on the scale would be nearly invisible compared to eating 200 fewer calories at dinner or walking for 30 minutes.
The Caffeine Factor
At 200 mg per can, a single Celsius uses up half the FDA’s recommended daily caffeine limit of 400 mg. Two cans put you right at the ceiling. If you’re also drinking coffee, tea, or pre-workout supplements, it’s easy to overshoot that threshold without realizing it.
Too much caffeine can cause jitteriness, insomnia, increased heart rate, and elevated blood pressure. Research on energy drinks with similar caffeine content has shown they can raise systolic blood pressure by about 10 mmHg and increase heart rate by 5 to 20 beats per minute. For most healthy adults, one can is unlikely to cause problems. But stacking it on top of other caffeine sources, or drinking it late in the day, can disrupt sleep. Poor sleep is one of the most reliable drivers of weight gain, so a Celsius habit that interferes with your rest could actually work against your goals.
Sugar-Free Doesn’t Mean Metabolically Neutral
Celsius contains only about 5 calories per can and uses artificial sweeteners like sucralose and acesulfame potassium instead of sugar. That’s obviously better than a 250-calorie sugary soda if you’re watching calories. But “zero sugar” isn’t the whole picture.
Animal research published in the journal Nutrients found that chronic intake of sugar-free energy drinks produced signs of insulin resistance, elevated blood sugar, and higher triglyceride levels comparable to their full-sugar counterparts. A separate randomized controlled trial in humans found that four weeks of sucralose supplementation decreased insulin sensitivity and blunted the body’s acute insulin response. These findings don’t mean a single can will wreck your metabolism, but they do suggest that relying on sugar-free energy drinks as a daily habit may carry metabolic trade-offs that aren’t reflected on the nutrition label.
Where Celsius Might Actually Help
The most realistic benefit of Celsius for weight loss has nothing to do with thermogenesis. It’s the caffeine boost before a workout. Caffeine is one of the most well-studied performance enhancers in sports nutrition. It can reduce perceived effort during exercise, improve endurance, and help you push harder in a training session. If drinking a Celsius 20 to 30 minutes before the gym means you run an extra mile or add another set of squats, the calories burned from that additional work will far outweigh the drink’s thermogenic effect.
A company-funded 10-week study looked at participants who consumed Celsius before supervised exercise sessions compared to a control group doing the same workouts without the drink. The Celsius group showed favorable changes in body composition. But it’s difficult to separate the caffeine’s performance-enhancing effect (which you could get from coffee) from anything unique about the drink’s other ingredients.
The Bottom Line on Celsius and Weight Loss
Celsius is a low-calorie energy drink with a moderate dose of caffeine. It will temporarily increase how many calories you burn, but the magnitude is small enough that it won’t make a noticeable difference unless the rest of your diet and exercise routine are already dialed in. Think of it as a potential 2 to 3% assist on top of the habits that actually matter: a calorie deficit, regular exercise, and adequate sleep.
If you enjoy the taste and use it as a pre-workout pick-me-up, it’s a reasonable choice compared to sugary alternatives. If you’re buying it specifically because you think it will melt fat, you’re paying a premium for what is essentially a caffeinated beverage with good marketing. A cup of black coffee with a squeeze of lemon and a piece of fresh ginger would give you most of the same active compounds for a fraction of the cost.