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“Just as it is difficult to determine the impact of changes in diet on body weight and body fat mass without considering exercise, these results suggest we cannot determine the impact of exercise on total fat oxidation and body fat mass without considering diet.” Edward L. Melanson, PhD, et al, Journal of Applied Physiology (October 15, 2009)
“Our intervention study has clearly demonstrated that when exercise is carried out, people experience beneficial physiological and psychological effects independent of any effect on body weight.” British Journal of Sports Medicine (November 1, 2009)
More Talk Back on Exercise and Weight Control
Stuck in the So-called Fat-Burn Zone
We recently challenged a TIME magazine cover story that said exercise doesn’t help with weight loss. The author asserted that exercise caused him to overeat and actually kept him from losing weight. We quoted experts to the contrary and offered other reasons that might account for his trouble losing the last few pounds. We explained how high-intensity intervals might solve his tummy fat problem. Finally, we told about a new study from the University of Colorado at Denver showing how treadmill exercise conditioned formerly obese rats to burn fat and “defend” a lower body weight. http://www.cbass.com/Time.htm
Now, we have two more studies parsing the effect of exercise on weight control, one reported in the British Journal of Sports Medicine (most recent version November 1, 2009) and the other from the same Colorado lab that produced the rat study showing how exercise works to control body weight.
I have a suggestion for the Colorado researchers for maximizing the impact of exercise on body composition. To my mind, their new study, reported October 15, 2009 in the Journal of Applied Physiology, demonstrates why training in the fat-burn zone doesn’t work very well. Let’s start with the details of that study.
The scientists from the UC School of Medicine provide evidence why people often don’t achieve significant weight loss from exercise alone. Led by Edward L. Melanson, PhD, an associate professor in the division of endocrinology, metabolism, and diabetes, they recruited three groups of people. One group was made up of lean endurance athletes; another group was sedentary and lean; the last was sedentary and obese. All subjects spent two separate 24-hours periods in a specially designed calorimeter room that measures the number of calories burned and whether the calories came from fat or carbohydrates. During one 24-hour period the subjects were sedentary (mimicking normal free-living activities); the other such period included an hour-long bout of stationary cycling.
Obesity, leanness, and aerobic fitness all impact the fat-to-carb burn ratio. Evidence suggests that obesity impairs fat oxidation (fat burn). Fat oxidation in muscle tissue from obese individuals has been found to be lower than fat oxidation in muscle from lean individuals. Endurance training is known to enhance fat burn. Poorly conditioned people tend to be sugar (carb) burners. At the other extreme, well-conditioned marathoners are able to burn a high proportion of fat for the entire 26+ miles.
Obviously, the researchers expected to see a difference in the fat-to-carb burn ratio in the three groups. They were especially interested in observing how each group apportioned and used calories after the hour of cycling (afterburn). Exercise is thought to “rev” up the metabolism, and keep it revved up afterward, as the body stabilizes and restore itself.
To encourage fat burn during and after cycling, intensity was deliberately kept relatively low, at about 55% of each subjects measured capacity. High-intensity exercise demands the quick energy provided by carbohydrates. They wanted to keep the subjects in the so-called “fat-burn zone.”
To their surprise, none of the groups, including the lean endurance-trained athletes, experienced afterburn. What’s more, the subjects did not burn additional body fat on the exercise day compared to the sedentary day. Exercise made no difference. (Please keep reading.)
Importantly, energy balance was maintained during the experiment. A greater proportion of fat calories was burned during the exercise day, but additional calories were consumed to restore energy balance. The aim of the study was to compare the effect of exercise alone on the three groups. The bottom line is that exercise made no difference—when energy balance was maintained.
“The message of our work is really simple,” Dr. Melanson said, “It all comes down to energy balance,” or calories in and calories out. Exercisers “are burning only 200 or 300 calories” in the typical 30-minutes session. “You replace that with one bottle of Gatorade,” Melanson observed.
The researchers concluded that exercise—and calorie deficit—are required to achieve weight reduction. “It appears that the state of energy balance is an underappreciated factor determining the impact of exercise on fat oxidations,” they wrote. (Is that really news?)
So, exercise didn’t aid weight loss—under the circumstances of this study. The study does not challenge the effectiveness of exercise combined with diet to achieve a calorie deficit—and weight loss. As shown in the above referenced rat study, exercise appears to make it easier to create a calorie deficit—and “defend” a lower body weight.
Out of the Zone
Here’s my suggestion. Breakout of the fat-burn zone!
It’s irrational to expect metabolism to be revved up after exercise if it isn’t revved up during the exercise. High intensity exercise—out of the zone—doesn’t burn proportionally more fat, but it does burn more total calories. As Dr. Melanson says, “It all comes down to energy balance,” or calories in and calories out.
Not only is this my opinion; it’s a fact. Professors Jack H.Wilmore and David L. Costill addressed this issue some years ago in their textbook Physiology of Sport and Exercise: "Low-intensity aerobic activity does not necessarily lead to a greater expenditure of calories from fat. More importantly, the total caloric expenditure for a given period of time is much less when compared with high-intensity aerobic activity."
To illustrate they give the example of a 23-year-old woman who exercised for 30 minutes at 50% of her VO2 max on one day, and for 30 minutes at 75% on another. The total calories from fat were the same—in both sessions she burned 110 calories of fat. Most importantly, however, in the higher intensity workout she expended about 50% more calories for the same time period--220 total calories for the 50% intensity workout and 332 for the 75% session.
For an average 40-year-old male the calories from fat would be about 145 in both sessions, but the total calories burned during the higher intensity workout would be 435 compared to only 290 in the low-intensity session, again 50% more. That's a big difference and over time the higher-intensity sessions will produce significantly more fat loss.
I asked Dr. Robert Robergs, director of the Center for Exercise at the University of New Mexico and co-author of EXERCISE PHYSIOLOGY: Exercise, Performance and Clinical Applications (Mosby, 1997), about low intensity versus high intensity for weight control. He agrees with Wilmore and Costill. "You can't convert a relative contribution to an absolute value,” Robergs told me; “it's the total amount of calories [burned] that's most important."
"There is another issue too," Robergs added, which makes the intensity of the workout important for fat loss. A more intense approach, he explained, "is more conducive to improving the muscle's ability to use fat." The more fit you become, the more likely you are to use fat as fuel. "When you become more fit you are just better able to metabolize fat for any given activity you do," Robergs stressed. (Dr. Melanson and his colleagues agree; see above.)
It also seems logical that high-intensity exercise would be more likely to produce an “afterburn” during the post-exercise period. I can’t prove this, but there is evidence that exercise makes it easier to create the calorie deficit that Melanson quite correctly says is essential for weight reduction.
This was first demonstrated in 1954 by world-renowned nutritionist Jean Mayer. He reported that animals exercising for periods of 20 minutes to one hour per day ate proportionally less than non-exercising animals. He concluded from this and other studies that when activity falls below a certain minimum level, food intake does not drop a like amount--and fat begins to accumulate. Apparently, this is one reason why the average person gains fat every year. A sedentary lifestyle throws the body's appetite control mechanism off, causing us to eat more calories than we expend. That's not to say that lumberjacks, marathoners, bodybuilders and other very active people eat less than sedentary individuals. They eat more, of course. The difference is that people who exercise have an easier time balancing calorie intake and energy expenditure. Dr. Robergs notes, for example, that Tour de France cyclists maintain or lose weight consuming more than 5000 calories a day.
Researchers may disagree on the precise role of exercise in weight control—Melanson and his colleagues say the primary benefit “may be in preventing…regain of fat mass after weight loss.” Everyone, however, agrees that the health benefits are many.
That brings us back to the new study reported in the British Journal of Sports Medicine, which examined the benefits of exercise apart from weight loss. “Exercise is widely promoted as a method of weight management, whilst the other health benefits are often ignored,” the report stated.
Benefits Beyond Weight Loss
Researchers from Australia and the UK, led by Neil King, Queensland University of Technology, Brisbane, Australia, recruited 58 overweight or obese men and women for a 12-week supervised aerobic exercise program. The regimen called for five workouts a week at 70% of heart rate maximum; each session was designed to burn 500 calories. Body composition and waistline changes were measured at the beginning and end of the study, along with changes in aerobic capacity, blood pressure, and psychological response.
The men and women were instructed not to restrict their food intake; they were to eat as usual.
To the surprise of some, the mean weight loss matched the predicted weight loss. On average, the participants lost a little over seven pounds—or a little more than one-half pound a week. About half of the subjects lost more, and the other half lost less. More precisely, the half classified as “responders” lost an average of 11.47 pounds, a pound a week. “Non responders,” on the other hand, lost only two pounds on average. Remember, no effort was made to create a calorie deficit; some of the participants may have responded to exercise by eating more. As noted, exercise sessions were supervised; compliance was good for responders and non-responders alike.
Even the non-responders, however, saw significant improvement the health measures, including aerobic capacity, systolic and diastolic blood pressure, waist circumference, resting heart rate, and positive mood. (Get this) “Although the difference in weight loss between the [responders and non-responders] was statistically significant, there was no statistically significant difference in health benefits.” (Emphasis added) In fact, non-responders with hypertension showed significantly more improvement in systolic (-6 vs. -15) and diastolic (-4 vs. -10) blood pressure. Moreover, those lagging in weight loss showed a marked increase in positive mood, “which was maintained during the 12 weeks.” The “acute improvement in psychological state” began almost immediately, before any noticeable weight loss could occur. The psychological benefits of exercise were almost instantaneous.
Feeling better psychologically is important, because other health markers are likely to go unnoticed. People know when they lose weight or their clothes are looser, but are usually not aware of a drop in blood pressure. Reduction in waist circumference—even in non-responders—is important for the same reason.
The researchers concluded: “These data demonstrate that significant and meaningful health benefits can be achieved even in the presence of lower-than-expected exercise-induced weight loss. A less successful reduction in body weight does not undermine the beneficial effects of aerobic exercise. From a public health perspective, exercise should be encouraged and the emphasis on weight loss reduced.”
I wonder about the wisdom of reducing the emphasis on weight loss. The prospect of weight reduction will motivate some that won’t be moved by the promise of health benefits. Exercise is a win-win proposition. Exercise regularly—and pay attention to what you eat—and you’ll lose weight and be healthier. Exercise and eat whatever makes you happy, and you’ll still come out well ahead.
In the words of the study, exercise alone will bring “changes in overall physical and psychological well-being.” Even if you lose less than you hoped, you’ll feel so much better that you probably won’t care. (It's hard to beat the spent-calm after training.)
Importantly, the researchers are in no way giving up on exercise as a means of weight control. “The results do not mean that exercise is fruitless or ineffective in the battle against obesity,” they add at the end of their report. “Overall, exercise can help to check weight gain, and in some people it is effective. Others need additional help to deal with any compensatory response.” In other words, they need to recognize the exercise does not provide a license to overeat.
As this British study demonstrates, separate and apart from weight loss, exercise produces tangible results. What’s more, exercise combined with sensible eating brings weight loss and more. It works wonders. (See The Miracle of Movement: http://www.cbass.com/MiracleMovement.htm )
Whatever you do, exercise!
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