Dear Dr. Katz:
Barbecue season is coming. So is bathing suit weather. If I overeat, how long does it take those calories to turn into pounds on my hips and thighs? And is there anything I can do to interfere with that process?
How long it takes extra calories to alter your shape varies with your rate of digestion, your diet (sugary drinks are digested very quickly; high-protein foods such as meat relatively slowly), and your age, since metabolism slows as we age. But in general, excess calories begin finding their way to your hips approximately four to eight hours from the start of a meal.
When you eat, a certain number of calories go to keeping your heart, lungs, organs and muscles working. This energy burn is your basal metabolism. For the average woman, it's about 1,200 calories a day. Additional calories go into two types of storage. The first is a roughly 1,000-calorie reserve of ready-to-burn energy called glycogen and it's stored in the liver and muscles. That reserve fuels activity such as walking, jumping, running and even fidgeting. Once the reserve is depleted, your body uses calories taken in by eating to replenish it. When the tank has been topped off, extra calories are then converted for long-term storage into fat molecules called triglycerides.
This means that if you overeat at dinner by, say, 700 calories, your hips could be carrying an extra one-fifth pound of fat by the next morning. Follow that pattern five days in a row, and you'll add a pound. Do that daily for three months, and you'll gain about 18 pounds.
As for interfering with this process, there is just one way: Less barbecue, more barbell. If you're generally active throughout your day and then you exercise, you'll burn through your glycogen stores, forcing your body to turn to its fat reserves. Keep it up, and the pounds will come off. With the right balance, both the beach and the barbecue can be your friends.