Great points ALG, on multifunctional activities instead of multitasking. Exercises are probably the most easily integrated healthy activities. I walk all distances within 45 minutes whenever possible, getting physical exercise as well as mental benefits (walking meditation), not contributing to pollution while saving some money as well. I have come to the aids of and saved a few lives along the way too while walking.
Many personal healthy practices benefit the world as well. Eat less, eat better. It will cut down obesity, leave more and better quality food for the world, preserve more nature, reduce cruelty to animals, and limit environmental damages and climate changes. As well, smaller people consume much less of other resources, from necessary material for accommodation and personal goods to demand on energy, requiring less fuel for food production, to keep smaller dwellings warm or cool, and to transport persons as well as goods. It will significantly cut down US dependence on foreign oil, curtailing wars (=huge reduction of suffering and damages!) Healthier population will greatly reduce medical costs and human resources for other pursuits of advancements. As well, healthy people can contribute more to society and better take care of others instead needing cares themselves. Yes, perfect health has no down sides. It doesn't take from others but enables one to give more easily.
I do not support cancer industry and I figure the best thing I can do against cancer is to stay healthy. I don't drain resources that way. Each person on the healthy side makes the statistic difference of 2 between the two sides, healthy and cancer. That beats all the runnings and donations and other involvements, which would only draw the disease undesirably into my consciousness. No, I don't consider my good health a selfish immoral concern in any way. In fact, I help others regain their health, if they so desire. But I don't do cancer, or any other disease du jour.