Having reasonable fitness and BMI is an essential part of being a safe diver. Even as a recreational diver, you may have to deal with an unexpectedly strong current, tow a tired buddy, or simply carry your equipment to and from the entry point of a shore dive. Moreover, poor fitness and excess body fat are known to be a predisposing factor for decompression sickness. However, some divers may see regular exercise or calorie-counting as a chore and believe that just going for a dive is enough exercise in itself. But does scuba diving burn calories?
If so, it seems like a dream come true —diving is such an enjoyable experience that the notion that it may help to keep us slim and improve fitness is a tempting one. But is diving a good workout? Can you ditch the gym sessions and simply go diving with friends each week? What is the fact behind the scuba-myth?
First, scuba diving and solid physical health and fitness often go together. Many people who dive regularly already have an active lifestyle and, as a side effect, have good physical fitness. The relationship, particularly with professional divers, is symbiotic; the diver is fit since they need fitness to perform their role, and the diving (and the associated physical tasks of working as a professional diver) help to cultivate that. However, what is the reality for occasional divers? Is diving, alone, enough to keep you in shape?
Burning calories pre- and post-dive
Although diving — when conducted correctly — is relatively effortless in-water, the tasks surrounding diving often test a diver’s strength and fitness and more obviously burn the calories.
Carrying heavy equipment on your back to and from an entry point in the heat can be tiring. Some shore dives may involve walking a considerable distance over sand or uneven ground, raising your exertion level and pulse rate. You’ll burn even more calories if more bulky equipment, such as drysuits and twin-sets, form part of your set-up.
Once in the water, you’ll sometimes have to conduct a surface swim to the descent point, which requires cardiovascular exercise and, consequently, you’ll burn more calories.
Physical exertion is necessary on the reverse journey at the end of the dive as well. Unless the boat crew brings the diver back to deck level with a diver lift, he or she will need to lift their weight by climbing a ladder back to deck level or boarding a zodiac or dinghy and climbing back in.
Much like the thoughtless steps we record on a wrist-mounted step-counter during a normal day, each of these tasks burns calories without the diver consciously registering them — the movements are intrinsic to the dive.
Dealing with the unexpected
Plan the dive and dive the plan — we all know this mantra. However, sometimes things can go awry.
An adverse change in weather conditions can mean increased surf, surge or current. Thus, a diver might face a more physically challenging entry or exit from the water, or have to fin harder to make their way to and from a descent point. During the during the dive, they may have to push harder and increase their finning rate to avoid hazards or take shelter from water movement on the wreck or reef.
Dive buddies are another variable in the equation. If your buddy is less physically able than you, you may have to help carry their equipment, tow them to shore, or help them to get in and out of their gear if they become exhausted. These unplanned activities and physical struggles all burn calories. It’s no surprise that professional divers must pass a fitness test to ensure they can handle such circumstances.
By far the most prolific way we burn calories while diving is thanks to our body’s thermoregulation.
The human body’s core internal temperature is approximately 98 F (37 C). When the internal temperature rises or, in the case of in-water activities, falls, the body tries to adjust by using internal mechanisms to return the core temperature to homeostasis. The effect is analogous to heating a cold house in winter — you can do it by lighting a fire or turning up the thermostat on the central heating, but this burns more fuel.
The water that we dive in is always considerably cooler than the 98 F (37 C) of our body core. And, in combination with this, water is 800 times denser than air and draws heat away from our bodies approximately 20 to 25 times faster. A diving exposure suit doesn’t so much ‘keep you warm’ as simply delay the process of you getting cold in an alien environment. It is not uncommon to hear divers, even returning from a long dive in tropical waters, say they feel very cold. This is the beginning of hypothermia as the body’s internal systems struggle to fight internal temperature loss. For the body to compensate for the heat loss, we increase calorie consumption.
The cooler the dive and the more challenging the conditions, therefore, the more calories we burn.
Some diving agencies have researched the calories burned during a ‘standard’ scuba dive. PADI estimates that an average shore-dive in temperate water burns as much as 600 calories per hour. This is roughly equivalent to calorie consumption while jogging. Leisurely boat dives in warm, tropical waters are estimated to burn approximately 300 calories an hour, equivalent to hiking or a brisk walk. A dive day in the tropics, with three dives a day, therefore, burns about 900 extra calories, or about 40 percent extra for an average male. You can — if you’re on a calorie-controlled diet — even note the calories you burned in your logbook.
Scuba diving for weight loss
Given that an average person requires around 2000 to 2500 calories a day to maintain their weight, it’s easy to see why lots of repetitive diving can lead to weight loss. Even three dives a day on a tropical liveaboard can consume 36-45 percent of your usual calorie requirement.
So, the answer is yes — scuba diving does burn calories and you can lose weight when diving. But you must still expend more calories than you consume — diving is not a license to go wild at the buffet. It’s all about the energy balance. Should you dive to lose weight? No, you should dive because you’re passionate about it. The potential weight loss should be a bonus for an already fantastic sport.
Diving may help you to maintain a healthy weight and fitness. However, it’s not a workout. Each diver must still take responsibility for their health and fitness and work to ensure they are fit and healthy to be safe on each dive.