Obesity has been long considered a risk factor for decompression sickness (DCS). It has been based on findings in animal studies and epidemiological data in military diving. There was no data to confirm the same effects of obesity on incidence of DCS in recreational diving; however, there were some studies indicating a positive correlation between body mass index (BMI) and likelihood of venous gas emboli (circulating gas bubbles) after dive.
In a recent paper, Kaczerska D, et al. The influence of high-fat diets on the occurrence of decompression stress after air dives. UHM 2013;40(6):487-497, intended to test possible effects of high fat intake on risk of DCS.
Researchers have found that divers who reportedly consume a high-fat diet (greater than 100% of predicted needs; methodology of calculation not published) are more likely to experience “decompression stress” with decompression dives to 30 meters (98 feet) and 60 meters (197 feet). I have two major concerns about this study.
First, the “decompression stress” was estimated by monitoring venous gas emboli (VGE) using Doppler detector, but quantitative measures (bubble grade) were not presented. Instead, findings were reported binary as VGE detected or not. In fact, the hyperbaric chamber dive to 30 meters for 30 minutes did not cause VGE in any diver, which is quite unexpected. The dive to 60 meters caused VGE in 29 out of 56 divers despite 180 minutes of decompression. It is likely that VGE grade was very low. None of the exposed subjects developed symptoms of decompression sickness (DCS). The authors erroneously used the term “symptoms of decompression stress” for conditions when circulating gas bubbles were detected although divers felt perfectly normal. While there is general consensus that high VGE grade is associated with an increased risk of DCS, the same cannot be said for the low VGE grade. Indeed, it would be farfetched to conclude that findings described in this paper translate into an increased risk of DCS.
Another concern pertains to the grouping of divers used in the analysis. Although the high fat intake was the variable tested, the subjects were divided in two groups not based on the fat intake but rather on the response to decompression. Results would probably be very similar in either way, but the chosen approach raises suspicion of possible research bias.
What if the findings that high-fat diet increases probability of VGE postdive occurrence are true?
Recreational divers should not worry. The most significant factor that affects the outcome of decompression is the severity of exposure which is defined by depth and duration of dive, breathing gas, exercise, thermal effects and dynamic of decompression. The dive exposures used in this study are not representative of recreational diving. Previous data which indicated that obesity was a risk factor for DCS pertained to severe dive exposures, while recreational diving in recommended limits constitutes mild exposure. Decompression sickness in recreational diving is a very rare outcome and so far there is no evidence that diet or obesity measurably increases risk of DCS. Technical and commercial divers, on the other hand, may be exposed to severe dive exposure, and thus, obesity may add to their already increased risk of DCS.
Regardless of the type of diving, obesity increases risks of other diving injuries and obese divers should be aware of it. Divers and nondivers should consume a balanced diet and maintain physical fitness to mitigate risk of chronic diseases. Healthy lifestyle, which includes a balanced diet, helps to maintain working capacity and long-term health and wellness.