Healthy Weight Loss Part I: Shedding Fat to Make Race Weight

For a cyclist, appropriate weight is just as important as aerobic fitness, strength and skills. However, many riders under-perform in hilly races because they carry too much body mass. They hope to ride off their excess weight in time for race season, but no matter how much you train, there are realistic limits to the rate of weight loss. Understanding the possibilities allows you to plan so you can arrive at the starting line next season in optimal shape.

Exercise can enhance weight loss, but it’s not as simple as “exercise more, get lighter faster.” It’s easy to exercise a few hours every day and still gain weight. For each 100 watts you generate, you expend about 360 calories per hour. Extremely fit riders cruising at 300 watts can exercise away roughly 1,080 calories per hour. Local-talent racers cruising at 200 watts use about 720. That’s a ton of energy over several hours, but we can all too easily scarf 1,000 calories in just a couple minutes.

It’s a challenge to eat enough to maintain weight while doing daily five-hour rides, but if you munch through the rest of each day, whether that’s health food or junk, you can have positive net calories and weight gain. Not counting appetite-suppressing high-altitude activities or multi-day stage races, no matter how much you exercise, it is possible to absorb more calories than you expend over several days. Weight control requires some diet control even with high volume exercise.

Simply eating less isn’t an ideal weight-loss strategy for athletes. We must eat for recovery. Athletes who don’t properly refuel with the right nutrients can’t exercise day after day, nor will they get faster or stronger from training. The best weight loss strategy will also depend on whether you need to lose muscle mass or fat mass. If you come from a strength sport, have a physical job, have lifted weights for years, or just tend to be muscular, you’ll likely need to cut muscle as well as fat to be competitive in hilly road or mountain bike races. Look for an article about cutting muscle weight in the next issue of ROAD. The rest of this article deals with losing weight by reducing body fat.

Fuel Sources and Weight Loss

An exercising athlete uses a mix of carbohydrate, fat and protein as fuel. Exercise intensity and duration determine the exact percentage and amount of each that your body expends. Only fuel that is not replaced between workouts contributes to weight loss.

Carbohydrate for exercise comes from glycogen, blood sugar, and food consumed during training. Carbohydrates make up about 50 percent of calories expended at rest or during very light exercise, rising to above 90 percent during hard efforts. A body can store roughly 1,000 calories as glycogen and only a few calories of blood sugar. You cannot absorb carbohydrate as fast as you expend it when exercising. Thus when you deplete carbohydrate stores, quality training is over until you take a break to recharge. It is an error to count burned carbohydrate calories when calculating weight loss because expended carbohydrate must be replaced before the next quality training session.

Protein for exercise fuel comes from breakdown of muscle tissue all around the body, not just in the working muscles. In fact, muscles constantly release amino acids into the bloodstream. During prolonged exercise, the percentage of calories coming from muscle protein gradually increases, reaching roughly 15 percent of total calories once carbohydrate is depleted. If protein is not replaced after workouts, muscles gradually shrink. For overly muscular athletes, losing muscle mass is beneficial. Those who already have a cyclist-appropriate muscularity should replace metabolized protein daily.

After each exercise session, you need to replace the carbohydrate you have used before you can train effectively again. Fat need not be replaced, while the need to replace muscle protein varies from athlete to athlete. For an athlete to lose weight without compromising training, he or she has to expend and not replace fat and possibly muscle protein.

Fat and Exercise by the Numbers

Fat as exercise fuel comes primarily from small deposits in and near working muscles. Belly fat and other larger, subcutaneous (under the skin) deposits are mobilized slowly. They can replace the useful fat near the muscles during recovery, but don’t contribute much during exercise. The belief that you can exercise away large amounts of fat is a common misconception. An examination of the numbers reveals that exercise is a minimally effective way to lose fat.

Fat represents roughly 50 percent of calories used at rest, dropping to near zero as exercise intensity approaches or exceeds the lactate threshold. For a medium height male rider, resting fat burn translates to about two-pounds of weight loss per week, if the calories are not replaced. One pound of fat contains approximately 3,500 calories. You use perhaps 720 calories per hour cruising in your aerobic endurance zone, so you can burn a pound of fat every five hours, right? Actually, no. Unless you are starving, you never get more than 50 percent of your calories from fat, and the harder you exercise, the smaller that percentage becomes. A fit cyclist will get about 20 percent of calories from fat when riding at 60 percent of VO2Mmax, which translates to low in zone 2, close to 70 percent of maximum heart rate, or 80% of functional threshold power. With increasing exercise intensity, the percentage of calories from fat drops more rapidly than total expenditure increases, so 20 percent of total calories at endurance pace turns out to be close to the upper limit of possible fat burn rate. For our steady 200-watt rider, that’s approximately one pound of fat metabolized for each 25 hours of endurance riding. A World Tour pro doing 20-plus hours per week could conceivably lose 3 pounds of fat each week counting exercise and resting use. If you are riding about ten hours per week, figure on a maximum fat loss rate of 2.5 pounds per week. As you can see, exercise contributes to fat reduction, but not much.

The less excess fat you carry, the harder it becomes to restore glycogen between training sessions without rebuilding fat as well. Losing 2.5 pounds of fat per week without compromising training quality is possible only for people who are several tens of pounds above racing weight. As you get within 20 pounds of a good road-racing weight, one pound per week is more realistic. It’s rare to find athletes within 10 pounds of racing weight who can still lose more than one half pound of fat per week.

The Factors of Weight Loss

Assuming you consistently follow a good diet, realistic rates of weight loss depend on three main factors: How much you have to lose, whether you will be losing fat or muscle and how much you train. Most people will lose three to five pounds the first week on a stringent diet. Unfortunately, that rate of weight loss is not sustainable since it is not “real” weight loss. When you suddenly cut back on calories, you are likely to become glycogen depleted. A full load of glycogen, plus the water stored with it, weighs several pounds. Losing glycogen or water weight compromises training. You can lose a pound by reducing your glycogen stores without making training impossible, but you can’t do it repeatedly to lose more weight. The food in your gut takes eight to 48 hours to make the full trip. When you start a diet, the amount of food in the tube is decreased, cutting another few pounds. A diet that reduces your salt intake will let your body retain less water, reducing your weight. You can’t continue to lose weight by making your gut more empty or dehydrating more though, without drastically compromising training.

Once you are past the large, initial weight loss, the rate at which you can continue to lose fat depends slightly on how much you can exercise. Table 1 is a table of the minimum time it should take to lose various amounts of fat if you are able to train 10 or 20 hours per week and adhere to a good diet. If you know roughly how much fat you have to lose and you know when you want to be in racing shape, this table gives you an idea of the last time you’d want to start losing. Schedule two weeks with stable weight before racing so you won’t be weak from starvation when you compete. Remember that when you again eat to recover, you’ll regain a couple of pounds of glycogen and water, so aim to get a few pounds below your target weight before starting to eat normally. These are minimum times, and most riders will lapse occasionally, so unless you are within a few pounds of racing weight now, it’s better to start losing sooner than to wait for the last moment. Losing large amounts of fat takes months or years, even if you train full time.

Table 1: Weeks to Lose Various Amounts of Fat Weight

Weight Loss is Challenging But Possible

Many riders find that cutting fat and muscle mass to arrive at a competitive racing weight is much more challenging than developing strength, skills and aerobic fitness. Many try and fail to reach a target weight. Sometimes that’s because of poorly chosen diets, including foods that restore recently burned fat between rides. Some riders are frustrated by their rate of weight loss so they give up. Often, riders wait too long to start a good diet and commence eating more for recovery in race season before they make race weight. With a better understanding of what it takes to lose weight and how fast it is possible to lose, you can make a realistic plan to arrive in the racing season both fit and light. Don’t forget to check the next issue or ROAD for the skinny on muscle mass reduction.

Read more about weight loss in Part II of this Article: Shedding Excess MUSCLE to Make Race Weight

Scott Saifer, M.S. and the coaches of Wenzel Coaching manage all aspects of our athletes preparation for racing and other cycling endeavors. Our programs cover fitness, skills, psychology and weight management for optimum performance.