Come January, Britain launches a new campaign: walk a marathon in a month. The NHS wants people ambulating for 20 minutes daily, with vouchers and incentives for the committed. Retailers and companies are being brought into the scheme as well. The idea is simple: turn walking into a habit by making it attractive. India could do with some of that thinking. Walking remains perhaps the least noticed form of exercise here, even as diabetes, heart disease, obesity and kidney disease affect millions. We have had abhiyaans for cleanliness, nutrition, water and fitness. Why not one for the simplest exercise of all? No gym, no equipment. Just put one foot in front of the other