You might be tempted to go on an all-out fast at the start of the year, particularly if the holiday period was marked by excess. Try and avoid that temptation, nutritionists say, and if you are scaling back your intake, go about it with thought and care. Avoid extreme fasting, says German nutrition expert Regina Ensenauer. One way to start is eating a little less at your regular meals. "Paying attention to quantities is a tip that applies to all age groups," says Ensenauer, who is head of the In