Dr Jules Eden, dive medicine specialist and founder of e-med, answers divers' questions - as published in Sport Diver magazine:
Q - With my work I get the opportunity to have a health screen every 2 years, and I had one last week. I got the usual admonishment for being overweight (my diet is full of fast food, I'll admit), but on the blood tests they said I had "impaired fasting glycaemia". As far as I understand this is not diabetes, but an early warning sign that I might develop it. I'm a fair weather diver who just does a few dives on holiday, nothing too adventurous or deep. Will this have any implications for my diving?
A - There’s a sort of no-man’s land in blood sugar levels, between the upper limit of normal (usually 6.0) and the diagnostic value for diabetes (usually 7.0). Anyone who’s in this range is classified as having impaired fasting glycaemia, and 1-2% of them per year will progress to diabetes. You should have had an oral glucose tolerance test, or be due one, which is used to exclude diabetes, but even if this is normal, you’re still at higher risk of heart disease. Lifestyle changes are vital if you want to stave off full blown diabetes – less chips ‘n’ gravy and some old fashioned exercise would help to sort the weight out. You need a dive medical to assess your physical fitness for diving and it’s probable you’ll need an exercise ECG (some pounding on a treadmill whilst wired up) to make sure your heart’s up to it. Even shallow submersion causes a fairly significant increase in the heart’s workload, so we need to know it’s got the capacity to cope.
Q - I'm due to finish my instructor course in the next couple of months and have got myself into a bit of a panic about my weight. I've always been a big lad, a typical rugby forward shape, but I enjoy sport and don't sit around, so I think I'm quite fit. This whole BMI thing worries me - I don't want to sit the medical if I'm going to fall at the first hurdle. How do I work out my BMI, and if it's high, is that an automatic fail?
A - No need to panic - Arnie, Sly and Jonah Lomu would all be classified as obese by their BMI’s. The Body Mass Index (BMI) was originally invented by a Belgian statistician to look at the relationship between fat, height and weight in human societies. Although explicitly cited as being inappropriate for individual diagnosis, it became popular simply because it’s easy to calculate (see box). Unfortunately this situation has persisted and it is still the favoured method to assess body composition, despite not actually measuring body fat at all. Age, gender, race and physical fitness will also skew the figures. In fact, the best marker of health risk is simply waist circumference – carrying fat round your middle is associated with high cholesterol, future heart disease and diabetes. The risk rises with waist measurements over 32 inches in women and 37 inches in men.
As far as divers are concerned, I’m more interested in body fat percentage and physical fitness, as these are the key parameters that guide their underwater safety. If you don’t have excess fat (above 30% would be regarded as a reason for rejection) and can pass the step test, then we can show a little leeway with the BMI.
How to calculate your BMI Measure your weight (in kilograms) Measure your height (in metres) and square it Divide your weight by your height squared
Q - I had weight loss surgery a few years ago. The procedure I had was called gastric bypass. Ironically I sold my dive gear to help pay privately for the procedure, thinking I'd never need it again. But having the surgery gave me a new lease of life and I have been thinking about getting back into the water. Is diving possible? Would there be any risks, or limits on my depth? All I'm interested in is shallow recreational dives in warm water, nothing extreme. Hope you can give me some good news.
A - I think I can. Gastric bypass surgery has been around for nearly 50 years, so surgeons are well aware of the possible complications of the procedure. The pleasant-sounding “dumping syndrome” is the most troublesome – cold sweats, butterflies, bloating and diarrhoea after eating (particularly whilst watching any form of reality TV). Small meals low in sugar are the order of the day (which is the whole point). On the whole results are good and weight loss sustained. A newer surgical approach is to wrap a band around the stomach, the size of which can be adjusted by injecting or removing saline through a port placed under the skin. This can be done via keyhole surgery (“laparoscopically”) and is hence commonly called a “lap band”. In Europe we are also blessed with the similar variant “Swedish adjustable gastric band”. Aren’t we lucky people? One charming complication of this procedure is Productive Burping, the regurgitation of swallowed food. Slower eating and more thorough mastication normally sort this out. Ascent from a dive can cause some acid reflux which might be an issue with either of these procedures, but this can usually be treated with antacids or similar drugs. Air trapping is unlikely as the gut is still “open” at either end for the important release of expanding gases. So assuming you have none of the above problems, go dive.
Q - My doctor has agreed to put me on some medication to help me lose weight. I've been overweight for most of my life and whatever I do I can't seem to shift it. Over the years I've lost a bit with crash diets but the weight always ends up piling back on, often to more than where I started from. It's very frustrating. I have been a diver for more than 10 years but haven't dived for the last 2 due to kids and work. I really want to get back in the water, to get fit again. Are there weight loss drugs that are safe to dive with? Any other advice?
A - I would imagine that with children and work commitments there’s been little time for exercise in the last 2 years. Diving is not the best form of exercise to get you fit; it will put strenuous demands on your system, so getting back some semblance of physical fitness should be your first goal. Swimming, cycling, and aerobic or cardio gym workouts would be my suggestions.
As for the weight loss medications, they vary in their modes of action and side effects. One called orlistat (XenicalTM) reduces absorption of dietary fat (giving rise to the mouthwatering “oily stool”) and if you can stomach the side effects, you can dive safely on it. Another called sibutramine (ReductilTM) acts on the brain to reduce cravings and hunger pangs. It works in the same way as some antidepressants, and is therefore subject to all the caveats of that class of drugs. Rather than relying on pills, however, I would encourage you to perservere with diet and exercise as this is really the best, safest and most sustainable way forward.
Q - I get a lot of students wanting to learn to dive who are overweight, and some hugely so. What are the real risks of diving if you are overweight, and how can I decide which ones are safe to train and which ones aren't?
A - Obesity is a huge topic (haha). Chocolate taxes, fire crews being called out to rescue 30 stone people stuck in the bath, a third of us obese by 2012… the media is full of fat. Briefly, the major issues with diving are:
1. Increased risk of DCS: nitrogen loves dissolving in fat. Obese divers will produce bigger bubble loads, which can overwhelm the normal lung filter and force bubbles into the systemic circulation. This puts them at higher risk of all forms of DCS.
2. Increased risk of diseases such as high blood pressure, diabetes, heart attacks and strokes. Every year dive accidents occur as a result of these conditions.
3. Decreased physical fitness tends to go hand in hand with being overweight, meaning it’s going to be harder to rescue yourself or your buddy. It also leads to higher risks of panic and more gas uptake on exertion (increasing DCS risk again).
4. Decreased lung function: sheer belly bulk can significantly restrict lung capacity, and overweight divers have lower oxygen levels, and higher carbon dioxide levels. In extreme situations these gas disturbances can cause breathlessness, confusion, and ultimately drowning.
A little bit of fat is good for you of course: it helps insulate you against the cold and cushions the internal organs. The much maligned BMI is still the best lay guide to body fat: square your height in metres, and divide that into your weight in kilos. If the result is over 25 then you’re overweight, and if it’s more than 30 then you’re officially obese. There are lots of caveats around this method, but if you’re worried about training someone because of their weight then just contact your local dive doc to discuss it.
Q - Hi doc. I think I know what the answer to this will be, but I'm going to ask anyway. I'm in the middle of my divemaster and want to eventually do the instructor course. I know I need the HSE medical to work in the UK, but I'm overweight and don't do any exercise at the moment. Will I pass? If not, what's the best way to lose weight, and is there a cut-off point to aim for?
A - Will you pass? That depends on how unfit and how heavy you are. The HSE issued new guidance on this last October, which tightened up the parameters somewhat – there are now flowcharts to aid interpretation of the measurements, which you can see on their website. The LDC dive medical pages have been updated with the changes too, so it would be well worth looking at these before making an appointment. In essence, once the BMI (Body Mass Index) reaches 30, we’re obliged to take waist circumference into account, and need to reject those in whom it exceeds 102cm (men) or 88cm (women). At this level and above, physical fitness usually suffers as well, and the step test we use now has strict cut off points too. In truth it’s this rather than the absolute BMI value that fails people, so if you’re not doing any exercise then I’ll let you draw your own conclusions as to whether it’s worth attempting the medical now.
The abundance of miracle weight loss cures on the net suggests that few, if any, of them actually work. It’s a simple sum really: if calories out exceed those in, you’ll lose weight. This translates to diet and exercise – no short cuts I’m afraid. In some circumstances medications or surgery are justified, but without knowing more details of your situation it’d be wrong of me to suggest these. A couple of tips though: rather than watered down soup for eternity, make dietary changes that you can stick with, and try and build some exercise into your daily routine, so that it doesn’t all go to pot once the new gym fad wears off. Best of luck.
Q - I weigh 13st 4lbs and am 5ft 3ins. My BMI is 32. Obviously, this is above the '30' acceptable limit for the HSE medical. However, I have a large excess of 'spare skin' as a result of a large amount of weight loss (7 stone in the last 12 months). I have been told I could get it removed (it was estimated by one surgeon that I have about 14-21lbs of extra 'skin'). However, I am not too keen to go under the knife for cosmetic reasons.
Am I wasting my time trying to become a UK Divemaster, in that I would not pass an HSE medical?
My weight has been steady now for the past 12 months - I don't think there is much chance of me losing much more weight.
I am already a Master Scuba Diver and have experienced no problems. My own GP has no problems with me diving - he thinks it is fantastic that I have found a physical activity that I have really taken to!
Your advice would be most gratefully received (I have nearly completed all of the written part of my DM Training!)
A - BMI is now perceived by the medical profession to be a rather outmoded measure of body composition. It has actually been around since the early 1800’s, and was meant to be a simple way of classifying people’s fatness or thinness. There are numerous factors that distort its accuracy: fitness level, muscle mass, age, gender, ethnicity, to name but a few. Most of the England rugby team would be likely to exceed the BMI of 30 that is often taken as the cut-off for “obese”. Its value in the HSE medical is to flag up those who are likely to be unfit, or more susceptible to DCI, as there are links between obesity and both these factors. So rather than automatically disqualify those with a BMI of above 30, it is more sensible to look at more accurate measures of body fat (such as impedance or skin calipers), and to look at fitness level closely. If these are satisfactory then there is discretion in our ability to pass suitable individuals. After all, we are mainly concerned with in-water safety – being able to fin over to a buddy or student in trouble, for example. So concentrate on the fitness, don’t be tempted to go under the knife for the sake of cosmetics, and listen to your GP’s (very sensible) advice.
Q - I would like to learn how to dive this year but would like to know what the weight/fitness requirements are. Basically I would like to dive and am using this as an incentive to lose weight.
Also what are the swimming requirements?
A - Like they say, if you drink and smoke less than your doctor, you are in pretty good health. So, if you are fitter and less fat than your dive doc, you'll be fine to dive.
So bad luck everybody, I am 75kg, can run a marathon in under 2 hours and am dead hard too. Enough of the lies, seriously, it's not a question of your weight, but fitness is the really important factor. If you can do 120 step ups to 18 inches in under 5 minutes, without collapsing then you will be fine. If your pulse then returns to a normal pre-exercise rate in, say 4-5 mins, then you are good enough to be a pro.
The issue with weight is that it is normally associated with fitness, but we all know heavy people who are fitter than a butcher's dog. The Pontypool front row for example. I wouldn't tell them that they couldn't dive as they weighed over 16 stone.
As for swimming, things have changed since my day. A swim for 200m is needed as part of the open water course I believe. You have to pass that, though I've got to say I have never swimmed in my life as a diver. Bobbed, drifted, finned yes. Swam, no. so don't get too hung up on being the next Thorpedo before you dive.
Now, you want an incentive to lose weight. Try this. For every kilo above 80, you have to earn a million a year before a supermodel will date you.
Q - Please can you tell me what my BMI needs to be below for an HSE Medical?
A - This is a very interesting point as there are several guidelines involved, but also the question of how accurate is the BMI or Body Mass Index as a measure of obesity.
The standard BMI under which you have to be is 30. If you are above this when you learn to dive then you are passed on to a medical referee who will assess your general health and wellbeing.
In BMI terms 30 is the break point above which you are considered obese, below 30 and above 26 you are overweight and below this healthy.
The reason BMI is important if you dive is like any other sport, if you are obese then there is a greater chance of all the knock on effects such as cardiac problems. This is why you are referred on to a referee to see whether you are a risk to any diver underwater and also if your fitness is going to pose a risk.
There used to be a thought that bodyfat released nitrogen at a slower rate and so would increase the chance of DCS too. However the evidence for this is fairly scanty so this is not really a factor in the equation.
Having said all of this though I do have personal reservations about the accuracy of the BMI. Basically it is calculated as a ratio of height to weight but the charts that doctors use are the same for men as for women but more importantly they do not take into account body morphism. This is a factor where some people are naturally very big and often their BMI comes out as obese when in fact they are obviously healthy and fit.
For example a prop forward in a rugby team may well be 5 foot 8 and weigh 16 stone, but he would have the same BMI as a woman of the same height and weight who hadn't done any exercise for the last 10 years and whose only past time was eating pizza and drinking cider. So would they both have to be referred to a medical referee?
Of course not. So you can see the problems involved with BMI. Perhaps in the future the body fat monitors will increase in accuracy and be used as the standard to pass or fail a diver.
But for now if you are below 30 you should be fine, above it you will be fine so long as you are fit and you have a strong and healthy cardiovascular system.