Obesity, Fitness and Diving

January 13, 2015 4:22 pm / Category: Business , Rebreather Diving

It is not a secret that obesity is a growing problem in the United States. Obesity is getting daily exposure on the TV networks, radio stations, newspapers, and magazines. While standing in the supermarket checkout line, one is tempted to read magazine headlines promising wonder-diets and exercise routines to transform the overweight in only a few weeks. Unfortunately, it is not that easy. Is that bad news for the overweight diver? Is diving detrimental to being overweight? This article is trying to answer those questions.
Obesity increases the risk of a number of health conditions including high blood pressure, high cholesterol, as well as other lipid concentrations, and type-2 diabetes. High blood pressure and high cholesterol can lead to atherosclerosis (clogging of the arteries) and heart disease. Stroke is another risk factor associated with high blood pressure. Diabetes affects all vessels and causes heart disease, loss of limbs, eyesight, and kidney function. Another big but underreported problem with being overweight is the potential for sleep apnea. As we fall asleep the tissues in the back of our throats relax. Most overweight individuals have excessive tissues around and inside their necks. The relaxation from falling asleep causes a collapse of those tissues leading to an obstruction. This results in excessive snoring and belly breathing, without actually being able to inhale and exhale effectively. Individuals with sleep apnea usually feel tired after a night’s sleep, have difficulty concentrating, and feel sluggish throughout the day. They are also at high risk of falling asleep behind the wheel, as well as for stroke and heart disease.
Adult Obesity Facts[1]
Obesity is common, serious and costly
  • More than one-third of U.S. adults (35.7%) are obese. Obesity-related conditions include heart disease, stroke, type 2 diabetes and certain types of cancer, some of the leading causes of preventable death.
  • In 2008, medical costs associated with obesity were estimated at $147 billion; the medical costs for people who are obese were $1,429 higher than those of normal weight.
Obesity affects some groups more than others
  • Non-Hispanic blacks have the highest age-adjusted rates of obesity (49.5%) compared with Mexican Americans (40.4%), all Hispanics (39.1%) and non-Hispanic whites (34.3%)
Obesity and socioeconomic status
  • Among non-Hispanic black and Mexican-American men, those with higher incomes are more likely to be obese than those with low income.
  • Higher income women are less likely to be obese than low-income women.
  • There is no significant relationship between obesity and education among men. Among women, however, there is a trend—those with college degrees are less likely to be obese compared with less educated women.
Between 1988–1994 and 2007–2008 the prevalence of obesity increased in adults at all income and education levels.
Between 1999–2000 and 2009–2010, the prevalence of obesity increased among men but not among women.
Between 1999–2000 and 2009–2010, there was an increase in the prevalence of obesity among boys but not among girls.
In summary, differences in obesity between men women diminished between 1999-2000 and 2009-2010 with the prevalence of obesity among men reaching the same level as that of women. In other words: Men are getting just as fat as women. Also, over the last decade there has been a significant increase in obesity prevalence among men and boys but not among women and girls overall.
Can You Be Fat and Fit — or Thin and Unhealthy? [2],[3]
A recent article in Time Magazine reported on a study based on 14 years of data from the Centers for Disease Control and Prevention. The study found that, when it comes to risk of early death, obesity by it-self is not as important as where on the body the fat is distributed. People of normal weight who had a paunch are metabolically more in danger to develop insulin resistance and inflammation. They were twice as likely to die earlier than people of normal weight without a gut. Moreover, people with excessive belly fat also had a higher risk of death than people who were simply obese all over.
“Weight is a major issue when it’s combined with a metabolic abnormality,” says study co-author Dr. Timothy Church, director of the Laboratory of Preventive Medicine at Pennington Biomedical Research Center in Baton Rouge. “When you have weight plus insulin resistance, weight plus hypertension, weight plus abnormal cholesterol — then you have an issue. Obviously the more overweight and the more obese you are, the more likely you are to have a metabolic abnormality.”
That being said, being obese does NOT have to be detrimental! According to the article in Time, “overweight and obese people were found to be at no greater risk of developing or dying from heart disease or cancer, compared with normal weight people, as long as they were metabolically fit despite their excess weight.”
The 2011 study by Lee, et al stated that maintaining or improving fitness is associated with a lower risk of cardiovascular mortality in men. Preventing age-associated fitness loss is important for longevity regardless of BMI change[4].
Compared with obese people who had at least two of the above markers of poor health, those who were obese but metabolically healthy had a 38% lower risk of early death from any cause. In fact, those who were fat but fit had no higher death risk than metabolically healthy normal weight participants.
Just because one is heavy does not mean that he or she is not also metabolically fit! Vice versa, thinner does not mean fitter! A lot of thinner people are in fact “skinny fat”. A term used to denote that overall body fat (particularly visceral fat) is still very high in some thinner looking people. Thus, just because someone is thin does not mean they are aerobically fit! People who diet but don’t exercise to lose weight may technically reach a “healthy” weight, but their fitness level is still poor. A person not physically active and resorting to unbalanced and restrictive diets, not only is unfit but is also metabolically unstable.
So the key message here for EVERYBODY thin or fat alike is: “Get more exercise!”
Diving and Fitness
The need for aerobic fitness becomes apparent when adequate physical reserves are critical in preventing small problems from becoming big problems. Numerous examples can be given here and we all have encountered at least one of them.
“The draw on cardiorespiratory systems begins with donning of gear and continues with water immersion and the concomitant shift of blood volume to the central circulation.”[5] What Pollock is referring to is that our pulmonary arteries and right heart chambers are experiencing a relative (or in some an absolute) volume overload of blood when we immerse in water. This may cause significant heart strain and for those who are already compromised, may worsen their cardiac condition. Pollock also noted that diving is not really a good form of exercise because diving does not typically include substantial aerobic demands. Of course there are exception to the rule such as long continuous swims, longer swims against currents, etc. On the flip side, using a scooter is like claiming Golf is great exercise when using a golf card or a caddy instead of carrying or pulling your own bag.
The suggested workout regiment for divers is three-times per week for 30-60 minutes per session of some physical activity achieving training intensity. To monitor intensity is to keep one’s age adjusted maximum heart rate to 55 – 75%. So take 220 minus your age to get to your age absolute maximum. From that, calculate 55 – 75% as your personal adjusted maximum target heart rate during your exercise sessions.
Obesity and DCS Risk
A more recent study found that irrespective of the experimental condition, there is a correlation between measured venous gas emboli and the subject’s age and body fat, respectively[6]. Several previous studies concluded that younger, slimmer, or aerobically fitter divers are known to produce fewer bubbles compared to older, fatter, or poorly physically fit divers. However, it was also suggested that fat content alone might not be the culprit of increased bubble formation but that the lack of exercise may be. Thus, adiposity may only be a surrogate indicator ([7]). Evidence supporting that conclusion came from studies in which most sedentary rats died compared to exercised rats during decompression ([8]).
Concluding Thoughts
  • Obesity alone is not an indicator of poor fitness
  • Obese individuals can become fit
  • Fit obese individuals may be at the similar health risk as fit normal weight people
  • Slim individuals may not be fit
  • Fitness is important to decrease mortality
  • Fitness is important to handle the stresses encountered during diving
  • Fit divers are less prone to DCS regardless of body habitus
  • Diving may not be a sufficient form of exercise
Offered to you by:
 Claudia L Roussos MD
Diplomat, American Board of Anesthesiology
Add Helium Dive Team
  1. [1] As per the CDC (Center for Disease Control and Prevention), 2011, http://www.cdc.gov/obesity/data/adult.html
  2. [2] Sifferlin A, Time Health and Family, 05/2012, http://healthland.time.com/2012/09/05/can-you-be-fat-and-fit-or-thin-and-unhealthy/#ixzz2KB2DroHC
  3. [3] Ortega et al, “Fitness and Fatness: not all obese people have the same prognosis”, Sept. 2012, http://www.escardio.org/about/press/press-releases/pr-12/Pages/fitnes-fatness-obese-people-different-prognosis.aspx
  4. [4] Lee et al, Long-Term Effects of Changes in Cardiorespiratory Fitness and Body Mass Index on All-Cause and Cardiovascular Disease Mortality in Men, Circulation, 2011: 124:2483-90
  5. [5] Pollock NW, “Aerobic fitness and underwater diving”, Diving and Hyperbaric Medicine, 2007; 37: 118-24
  6. [6] Brubakk AO, et al – The role of intra-vascular bubbles and the vascular endothelium in decompression sickness – review, Diving and Hyperbaric Medicine 2009; 39:162-9
  7. [7] Carturan D, et al – Ascent rate, age maximal oxygen uptake, adiposity, and circulating venous bubbles after diving. J Appl Physiol 2002; 93: 1349-56
  8. [8] Wisloff U, et al – Aerobic endurance training reduces bubble formation and increases survival in rats exposed to hyperbaric pressure. J Physiol 2001; 607-11