I subscribe to the AICR RSS feed and noticed they released their latest information on body fat and cancer on Friday! Since only aerodynamics rate higher on the Ironmans list of priorities I thought it would make a good blog.
They have combined two analysis, one estimating the percentage of deaths by cancer attributable to being overweight and the latest American cancer incidence data. In short they link 100,500 case of cancer per year to being over weight, which was as much as 49% of endometrial cancers.
The link between excess fat and cancer is well established now although the reasons behind it are less clear. One reason is hormonal regulation, fat tissue produces oestrogen which can promote the growth of some tumour and breast cancers. It is also associated with high insulin levels and can impair the immune system resulting in higher levels of oxidative stress. There are also associated lifestyle factors that are associated with being overweight like lack of exercise, something I’ll deal with in another blog but that also effects cancer incidence and outcome. This makes it hard to interpret the effect of being overweight in isolation.
What is also clear is that people aren’t taking on the health message as the population continue to get fatter. I have to be sympathetic to people trying to loose weight, it’s hard to change bad habits and eat well especially if you don’t burn an extra 3000 cal per day on triathlon training. It doesn’t help when people publish research showing that being overweight can help you live longer. Such research is often weak but leaped on by the media. Check out this CRUK cancer blog for more on that.
There should be a health warning for those dust bins among us however that think that just because they burn the energy they can eat whatever they want. A healthy diet is rich in fruit and veg and low in processed food such as meats that are high in sodium nitrite. While excess fat causes it’s own problems, undoubtedly the food choices that get you there play a role too.
All very true, but see Matt Fitzgerald, ‘Can Triathletes eat Whatever they Want?’ (Inside Triathlon 24.6): ‘Physically active persons who maintain a normal bodyweight can get up to 50% of their daily calories from fat…without exhibiting any of the adverse consequences that are associated with such a fatty diet in overweight, sedentary people.’ Fitzgerald certienly doesn’t advocate a junk diet for long-distance triathletes, but does suggest that ‘unhealthy’ foods are the only way to sustain healthy body weight when burning 3000 calories/day and argues that ‘among competitive endurance athletes, inadequate calorific intake is a more common problem than overeating.’ He cites several instances of world class athletes whose performance does not appear to be impeded by their poor/junk diets, though does caution that there is no research on whether these high fat diets will have negative long term effects.
Matt Fitzgerald has an excellent blog on nutrition although I can find that piece. The sports nutrition studies he tends to reference are not forward looking enough to tell how the diet will affect cancer incidence though. I would agree that getting 5000 cal per day with a normal diet is essentially impossible but I think we should try and make sure the foundation to our diets are sound and not replace the essential nutrient dense foods with rubbish telling ourselves it’s ok because we wont get fat. I’m no nutritionist but that seems like common sense.
Agreed!