New diet book: Fix your metabolism for weight control

• New book recommends 70 minutes a day of exercise to maintain weight loss
• Exercise burns calories and helps repair metabolism%2C book authors say
• Wear a pedometer and try to increase steps to more than 7%2C000 a day%2C they say

For years, obesity researchers James Hill and Holly Wyatt have been studying why so many people struggle with losing weight and keeping it off, and the two have concluded that a big part of the problem has to do with lack of physical activity and its impact on metabolism.

"Not everyone agrees with me, but I believe that obesity starts with a lack of movement," says Hill, founding executive director of the Anschutz Health and Wellness Center at the University of Colorado in Denver.

Studies show that when people stop being active, a host of different things happen that can lead to weight gain — their metabolism slows, their appetite goes haywire, and they begin eating too much of the wrong kinds of foods, says Hill, co-author with Wyatt of a new book, State of Slim: Fix Your Metabolism and Drop 20 Pounds in 8 Weeks on the Colorado Diet, written with Christie Aschwanden (Rodale, $26.99).

Metabolism is the process in which your body converts food to energy it can use, says Hill, It's more than just how many calories you burn — it's how you use different types of foods including protein, carbohydrates and fat.

Exercise keeps your metabolism working properly and your appetite balanced, Hill says, and he recommends working up to doing 70 minutes a day of moderate intensity physical activity — walking briskly, biking, swimming, playing tennis — six days a week.

What? Why so much exercise?

Not only will this amount of activity use extra calories during the exercise, but it's "the basic threshold of activity necessary to rebuild your metabolism so you can stop stockpiling fat and prevent unwanted pounds from creeping up on you," Hill says.

Here's the theory on metabolism and weight control outlined in the book: "When you have a flexible (healthy) metabolism, your body efficiently burns whatever kind of food you eat.

"When you have a inflexible (unhealthy) metabolism, your body doesn't switch very rapidly between types of fuel (carbohydrates, fats, protein), and it's during these periods when it doesn't switch quickly that your body accumulates fat," he says.

Say what?

To be clear, improving metabolic flexibility is not about boosting your metabolism so that you burn more calories while you're sitting down, but it allows your body to more efficiently burn whatever type of food you eat, lessening the chances you will add body fat, he says. "I think metabolic flexibility is going to be the next big thing in weight loss and weight gain. I think it's going to be more central to weight management.

"This is a concept that has growing support among obesity researchers, and we are seeing more and more studies about its link to obesity," Hill says. If you are currently overweight and inactive, you probably have an inflexible metabolism. To fix it and keep it operating at a high level you have to make physical activity a regular part of your day, he says.

Tim Church, director of preventive medicine research at the Pennington Biomedical Research Center in Baton Rouge, says, "Metabolic flexibility is a concept that can be difficult to grasp because people typically associate the word metabolism with the amount of fuel burned, not the type of fuel. I strongly agree that increasing your metabolic flexibility is likely to promote health and weight loss."

Nancy Clark, a sports nutrition counselor in Newton Highlands, Ma., says, "I agree with what Jim Hill is saying. In the real world, we rarely eat the exact right amount of calories, but our weight stays relatively stable, unless we mess it up by consistently overeating and/or under-exercising."

Hill and Wyatt base some of the ideas in their book on the habits of people in the state of Colorado, which is considered the leanest state in the USA because it has the lowest rate of obesity with about 21% of its residents who are obese.

The authors also draw from their work at the Anschutz Center as well as findings from the National Weight Control Registry, a database of more than 10,000 people from across the U.S. who have dropped at least 30 pounds and maintained the loss for at least a year.

The average participant in this registry has lost 70 pounds and kept them off for six years. Hill co-founded the weight control registry and founded America on the Move, a national initiative to get people to make walk more and make small changes in their diet.

Members of the registry do an average of about 60 minutes of physical activity every day, Hill says. The more weight you have lost, the more exercise you may need to do to keep it off, he says.

The authors recommend following one of two options for incorporating physical activity into your life:

- A structured plan in which you work up to doing 70 minutes of planned activity six days a week.

- A flexible plan. You eventually do 35 minutes of planned activity, combined with moving more in your daily life. You measure your lifestyle activity with a pedometer. Lifestyle activity requires more movement throughout the day including walking from your car into the office, climbing stairs, navigating the grocery store, chasing your child around the house.

You also can think of the activity in terms of the steps you take each day. Hill points out that a recent poll found that on average people in this country are taking about 5,500 steps a day. "This means we are a very sedentary society. This is not enough exercise to keep a healthy, flexible metabolism. Simply adding an additional 2,000-3,000 steps will help many lean people keep a healthy metabolism and avoid gaining weight. However, people who are obese with an inflexible metabolism seem to have to do more exercise — probably 10,000-11,000 steps a day to fix their metabolism and keep it healthy."

Hill says he doesn't want to "oversell" exercise. Dietary restriction is the key factor in losing weight, but exercise is the key to maintaining that loss. If dieters try to maintain their weight loss without exercise, it makes it practically impossible to relax their diet vigilance even a little, and constant diet vigilance is practically impossible, he says. "There is no way around it. The way to keep weight off has to include exercise."

Hill and Wyatt divide their diet plan, called the Colorado Diet, into three phases with food choices expanding during each phase.

The first two-week phase is "a quick way to get weight off," says Wyatt, who directs the Colorado Diet Center at the Anschutz Center. Dieters select from a list of lean proteins (chicken breast, turkey breast, fish, fat-free cottage cheese, lean beef, non-fat Greek yogurt); non-starchy vegetables (asparagus, broccoli, carrots, cauliflower, dark leafy greens) and healthy fats (almonds, olive oil, canola oil). In this phase, many people are just beginning to exercise.

Dieters add more foods in second and third phases as they build their exercise programs to 70 minutes a day.

Throughout the plan, the authors recommend that dieters: eat six times a day, have a meal or snack every two to four hours; have breakfast within an hour of waking up; measure portions; have the right carb and protein mix at every meal, eat a healthy fat twice a day.