Do hot tubs burn calories? The truth about losing weight while you soak
We have all had that wishful thought while relaxing after a long week. Wouldn’t it be nice if we could get fit just by sitting here?
It sounds like a dream. You sit back in the warm, bubbling water, close your eyes, and somehow the weight just falls off. For years, this idea was mostly a joke we told ourselves to feel better about skipping the gym. But recent science suggests there might actually be some truth to it.
Before you cancel your gym membership and buy a new swimsuit, we need to look at the facts. Do hot tubs burn calories? It is true that your body burns energy differently when you are hot. But how much difference does it really make? And is it enough to count as a workout?
This guide will walk you through exactly what happens to your body in a hot tub. We will look at the science, compare it to sitting on your sofa, and explain how to use heat safely.
Do hot tubs burn calories? The science
To understand how a hot tub burns calories, you have to understand how your body handles heat.
Your body is like a furnace. It constantly works to keep your internal temperature at a steady level (around 37°C). When you step into a hot tub, the water warms you up from the outside.
This is called “passive heating.” It means your body temperature rises without you moving a muscle.
When this happens, your body has to work hard to cool you down. It cannot sweat effectively because you are underwater. So, it relies on other methods. Your heart rate increases to pump blood to your skin. This helps release heat.
This extra work requires energy. Energy usage in the body is what we call burning calories.
Dr. Steve Faulkner and a team of researchers from Loughborough University in the UK decided to test this. They wanted to see how much energy we really use when we get hot.
Do hot tubs burn calories? The study
In 2017, the researchers at Loughborough University conducted a study that made headlines around the world.
They took 14 men and put them through two different tests. First, the men went cycling for one hour. Second, the men sat in a hot bath (40°C) for one hour.
The researchers measured how many calories the men burned in each session. They also looked at their blood sugar levels.
The results were surprising. Do hot tubs burn calories? Maybe!
Cycling obviously burned the most energy. But the hot bath was not useless. The researchers found that sitting in the hot water for an hour burned about 140 calories.
To put that in perspective, that is roughly the same amount of calories you would burn on a 30-minute walk.
This does not mean a hot tub is better than a walk. Exercise has many benefits that heat does not give you, like strengthening your muscles and bones. But it does show that sitting in hot water does more than just relax you. It makes your metabolism speed up.
Do hot tubs burn calories? Compared to the sofa
This is the big question. We know you burn calories all the time, even when you are sleeping. So, do hot tubs burn calories? Compared to just sitting in your living room?
Scientists use a unit called a MET (Metabolic Equivalent of Task) to measure effort.
Sitting quietly on your sofa watching TV has a MET value of about 1.0 to 1.3. This is the baseline. It is the lowest amount of energy you use while awake.
For an average person weighing about 70kg, sitting on the sofa burns roughly 70 to 90 calories per hour.
Now, let us look at the hot tub. According to the study mentioned above, heat increases your metabolic rate. Energy use rises to levels comparable to a gentle walk.
Here is the breakdown for a one-hour session:
Sitting on the sofa:
- Burn: Approx. 70 to 80 calories
- Heart rate: Resting (60 to 80 beats per minute)
- Sweat: None
Sitting in a hot tub (40°C):
- Burn: Approx. 140 calories
- Heart rate: Elevated (can rise significantly depending on heat)
- Sweat: Yes (though you might not feel it in the water)
The difference:
By choosing the hot tub over the sofa, you are burning an extra 60 to 70 calories per hour.
It might not sound like a lot. It is about the same as one digestive biscuit. But over time, these small numbers can add up. It is certainly better than nothing and answers the question, do hot tubs burn calories?
Factors that change your results
The number of 140 calories is an average. Your personal results might be different. Several things change how much energy you use.
Your weight
Heavier people tend to burn more calories than lighter people, even at rest. This is because their bodies have more mass to maintain. If you weigh more than the men in the study, you might burn more than 140 calories. If you weigh less, you might burn less.
The water temperature
The study used water at 40°C. This is quite hot. Most home hot tubs are set between 37°C and 40°C. If your water is cooler, your body will not have to work as hard to stay cool. This means you will burn fewer calories.
Duration
The study measured a full hour of soaking. Most people do not stay in a hot tub that long. If you only stay in for 15 or 20 minutes, you need to adjust your expectations. A 15-minute soak might only burn an extra 15 to 20 calories compared to sitting dry.
Your fitness level
Interestingly, fit people might handle heat better than unfit people. This could mean their heart rate does not go up as high, so they might burn slightly less energy. However, individual biology varies a lot.
Is it safe to use a hot tub for weight loss?
This is the most important section of this guide. While burning calories is great, safety must come first. Do hot tubs burn calories safely for weight loss?
Trying to overheat your body on purpose can be dangerous if you are not careful. The CDC (Centers for Disease Control and Prevention) provides clear advice on how to stay safe.
Here are the key rules you should follow.
Watch the temperature
Do not let the water get hotter than 40°C (104°F). Most modern hot tubs have safety locks to stop them from going higher. Higher temperatures can cause heatstroke, which is a serious medical emergency.
Limit your time
It is not recommended to stay in a hot tub for hours on end. Start with 15 to 20 minutes. If you feel dizzy, lightheaded, or nauseous, get out immediately. Your body is telling you it is overheating.
Stay hydrated
You sweat in a hot tub, even if you do not realise it. You can lose a lot of water very quickly. Drink plenty of fresh water while you soak.
Avoid alcohol
This is a big one. It is tempting to have a glass of wine or a beer in the tub. But alcohol dehydrates you. It also impairs your judgement. The CDC strongly advises against drinking alcohol before or during hot tub use. The combination of hot water and alcohol can make you faint, which is very dangerous in water.
Pregnancy warning
If you are pregnant, you must be very careful. Raising your core body temperature can harm the baby. The CDC says you should talk to your doctor before using a hot tub if you are pregnant. Many doctors advise avoiding them altogether or keeping the water much cooler.
Heart conditions
Because heat makes your heart beat faster, it mimics the effects of exercise. If you have a heart condition or high blood pressure, this extra stress on your heart could be risky. Always check with your GP before using a hot tub if you have heart concerns.
Other health benefits of the heat
Burning calories is not the only reason to enjoy a soak. The Loughborough study and others have found several other benefits to “passive heating.”
Blood sugar control
The researchers found that the hot bath helped keep blood sugar levels lower after eating. In fact, the hot bath was almost as good as cycling for controlling blood sugar peaks. This is promising news for people who struggle with their metabolism.
Lower blood pressure
Heat causes your blood vessels to widen. This is called vasodilation. When your blood vessels are wider, your blood flows more easily. This can temporarily lower your blood pressure. A study in the Journal of Physiology suggested regular hot baths could improve heart health over time.
Reduced inflammation
The same study suggested that heating the body might help reduce inflammation. Chronic inflammation is linked to many diseases, so anything that lowers it is a good thing.
Better sleep
A drop in body temperature helps you fall asleep. When you get out of a hot tub, your body cools down rapidly. This signal tells your brain it is time to sleep. A good soak an hour before bed can help you get a better night’s rest.
Do hot tubs burn calories more than the gym? Why does this not replace the gym?
We have established that you burn more calories in a tub than on the sofa. We have also seen that it can help with blood sugar.
Does this mean you can swap your running shoes for flip-flops? Sadly, no.
Exercise does things that hot water simply cannot do.
Building muscle
Sitting still does not work your muscles. You need resistance and movement to build strength and tone.
Bone density
Weight-bearing exercise (like walking or running) helps keep your bones strong. Floating in water does not help with this.
Cardiovascular fitness
While your heart rate goes up in the tub, it is not the same as training your heart through cardio exercise. You are not improving your stamina or lung capacity in the same way.
Think of the hot tub as a supplement to a healthy lifestyle, not a replacement for it. It is a great recovery tool. After a workout, the heat helps soothe sore muscles and joints. This might help you get back to the gym sooner.
Summary
So, do hot tubs burn calories? Yes, they sure do!
When you sit in hot water, your body works harder to keep you cool. This process burns energy.
You burn significantly more calories in a hot tub than you do sitting on the sofa. It is roughly equal to a gentle walk.
However, it is not a magic weight loss solution. You cannot undo a bad diet just by having a bath. The calorie burn is modest.
If you have a hot tub, enjoy it. Use it to relax, to recover from exercise, and to get a little boost to your metabolism. Just remember to stay safe, keep hydrated, and don’t cancel that gym membership just yet.
Frequently Asked Questions – Do hot tubs burn calories?
Can I sweat out fat in a hot tub?
No, you cannot sweat out fat. Fat is energy stored in your body. It is “burned” when your body needs fuel. When you sweat, you are losing water and electrolytes, not fat cells. You might weigh a little less immediately after a hot tub session, but that is just water weight. As soon as you drink a glass of water, that weight will return.
How long should I stay in to burn calories?
The study used a 60-minute session, but that is a long time for most people. For safety, it is better to stick to 15 to 30 minutes. You will still get some benefits without the risk of overheating or dehydration.
Does a hot tub help with cellulite?
Heat improves circulation. Better blood flow can temporarily make your skin look smoother and plumper. This might make cellulite look a little better for a short time. However, it does not cure cellulite or remove the fat deposits that cause it.
Do hot tubs burn calories more than a sauna?
Both hot tubs and saunas use “passive heating.” They both raise your body temperature and heart rate. Some people find saunas more intense because the air is hotter than the water in a tub. However, the effect on calorie burning is likely similar. It comes down to which one you prefer and which one you can tolerate safely.
Will I lose weight if I use a hot tub every day?
If you use a hot tub every day and change nothing else, you might see a very small change over a long time. Burning an extra 60 calories a day adds up to about 420 calories a week. To lose one pound of fat, you generally need a deficit of about 3,500 calories. So, it would take about two months of daily soaking to burn off one pound of fat, assuming you did not eat any extra food. It helps, but it is slow.
So, do hot tubs burn calories? Is it worth it?
Yes, they do burn calories, but is it a significant amount to lose weight? No, not really! We love our hot tub but know that the difference it makes to weight loss is minimal. That said, it is very good for mental health, and you can’t really eat in the hot tub, which I guess helps too!
