When addressing questions about metabolism and weight management, there are many misconceptions, even among professionals. Let’s address some of these myths.
Myth #1 - Eat more calories, lose weight.
Or phrased another way: If you eat less than your resting metabolic rate (RMR), your body will go into starvation mode, and you will stop losing weight.
RMR-based weight-loss programs are evidence that a person can consume below their RMR and still lose weight. In an eight week weight loss intervention, participants ate 70 percent of their RMR and performed either resistance or aerobic exercise. Average weight loss over the study period was nine kilograms. In a 12 week intervention program, participants ate 80 percent of their RMR and experienced a 6.7 kilogram weight loss.
So why does it seem that when you tell your client to eat more, they lose weight? It is very challenging to consistently (and voluntarily) follow a low calorie diet. A few days of eating restrictions may lead to one day of overeating. When you calculate the average calorie consumption for the week, you find the person is not actually following a low calorie diet. Choosing a calorie goal that is too low sets a person up for failure, not due to a starvation response but because it is too difficult to follow the diet consistently and have the energy to maintain a desired level of physical activity.
The Bottom Line
The fact remains that eating fewer calories than you burn will result in weight loss.
Myth #2 - My RMR can’t possibly be that high. I only eat 1,000 calories per day.
Research indicates that most people underestimate their calorie intake and overestimate their physical activity. People tend to underestimate their intake by approximately 20 percent. Underreporting can increase as body mass index increases, with overweight and obese subjects underreporting their intake by approximately 40 percent.
Just because a client seems very meticulous and honest about reporting their intake does not guarantee accurate reporting. Most people don’t correctly estimate portion sizes. If a client drinks a bottle of soda (20 ounces), they may report having one can (12 ounces). This small error leads to a 90 calorie difference. When a person orders a plate of spaghetti at a restaurant, they are getting three cups and likely report eating one cup or one serving. In this case, the reporting error results in a 400 calorie difference. Underestimating just a few foods a day easily amounts to a several hundred calorie difference and results in individuals not attaining their weight management goals.
Another reason people may not be consuming what they think they are is that they don’t record their food as they eat. At the end of the day, they may forget the handful of chips they grabbed while making dinner or the left-over food they ate off their child’s plate.
The Bottom Line
Underestimating calorie intake and overestimating calorie expenditure is common.
Myth #3 - My client gained a lot of muscle in a month, lifting two times per week. Their RMR should increase drastically.
RMR can be raised by increasing lean muscle mass. Most people do not lift frequently or intensely enough to impact RMR. In addition, when an untrained individual begins a strength training program, he becomes stronger by becoming more effective in using the muscle mass he already has, not always by "growing" muscle.
One study reports a seven to nine percent increase in RMR after a 24 week strength training session in men and women. Subjects participated in a whole body strength training program for three days a week, with exercises conducted at near maximal effort on all repetitions. Following the 24 week period, fat free mass increased by approximately two kilograms for young men and women (20 to 30 years old) and approximately one kilogram for older men and women (65 to 75 years old).
In weight loss, retaining muscle mass does not always result in maintaining RMR. In an eight-week weight-loss program, participants performed either resistance or aerobic exercise. Both groups lost equal amounts of weight, with the resistance trained group retaining more muscle mass than the aerobic exercisers. In other words, both groups lost muscle mass, but the resistance trained group lost less muscle mass than the aerobic group. However, both groups experienced an equal decline in RMR.
The Bottom Line
There are many benefits of weight lifting. Help your client set realistic expectations.
Myth #4 - My client cannot lose weight; therefore, she must have a slow metabolism.
Let’s explore two implications of this statement. The first myth is that many clients who cannot lose weight have slow metabolisms. Secondly, we assume we can label our clients as having a low or high metabolism.
Some clients may be surprised to find out what their RMR is. As stated in Myth #2, people often believe that they eat less and exercise more than they actually do. For a 180 pound client who is struggling with weight loss and believes she is following a 1200-calorie diet, her 1700 RMR reading may come as a shock. This is a good opportunity to help your client understand how easy it is to underestimate calorie intake.
Labeling your client’s RMR as high/low or good/bad may satisfy an immediate need to compare and categorize clients, but it isn’t accurate nor beneficial in the long run. Taking the example above, would you classify this client as having a high or low metabolism? It may be tempting to go back to an estimation equation and classify their number based on whether the measurement was higher or lower than the estimation. This logic is based on the false assumption that the estimated RMR should represent a normal RMR for your client. This is simply not the case. Estimation equations are largely based on populations that do not resemble your client. Comparing them to those populations is not an accurate way to determine whether they have a high or low metabolism.
Telling your client that her RMR is good because it is high can have negative consequences. If she improves her nutrition and exercise habits to lose weight, she is making positive changes to achieve her goal. Re-measuring her RMR, you find that it has dropped by 200 calories. Would you now classify her as having a low or bad RMR? Is she to assume healthy lifestyle changes have resulted in a negative outcome, despite her successful weight loss? A better approach is to tell your client that getting a measurement is good because it allows you to build an individualized nutrition and exercise program to meet her goals.
The Bottom Line
Knowing resting metabolic rate should be used to set your clients' calorie budgets, not to assess whether they have a “fast” or “slow” metabolism.
Myth #5 - I must exercise at a lower intensity in order to utilize fat and lose more fat weight.
Many people have been told that exercising at a low intensity – referred to as the fat-burning zone – will result in greater weight-loss from fat. It is true that the higher the intensity of exercise, the higher the percentage of carbohydrates (versus fat) burned for energy. But does this result in more weight-loss or increased weight-loss from fat sources?
The table below illustrates an example of a 150 pound woman exercising for 30 minutes at two different intensity levels:
||Walking (fat burning zone)
||Running (higher intensity)
|Percent from fat
|Calories from fat
|Percent from carbohydrate
|Calories from carbohydrate
In this hypothetical example, you find that:
- The percentage of fat calories burned is higher in the “fat burning” zone; however, the absolute number of fat calories is higher in the running example.
- The total number of calories burned is higher for the running example. The goal for weight loss is to burn more calories than you consume.
It all comes down to calories. The amount of body fat used from body fat stores is determined by the total number of calories burned and not the type of calories burned.
There is nothing wrong with exercising in this “fat burning” zone, as long as your clients understand that they won’t lose more weight in that zone, unless they exercise for a longer duration and burn more calories. One advantage of exercising at a lower intensity is to make the exercise more enjoyable to clients and increase their chances of adhering to the program. If your client quits after 15 minutes due to the discomfort of the running intensity, you may encourage him to walk one hour instead. This results in more calories burned, a more pleasant workout experience and client retention. If your client is pressed for time and able to run at a higher intensity, exercising in their "fat burning" zone may not be the most efficient use of time.
The Bottom Line
Total calories burned – not which zone your client trains in – determines amount of weight loss. Working out in a specific zone may improve certain aspects of cardiovascular fitness.
Just because something makes sense at first glance does not make it true. It is good practice to question long-held beliefs. Collect information from reputable sources to provide your clients with the best opportunity to succeed.
- Benezra et al. Intakes of most nutrients remain at acceptable levels during a weight management program using the food exchange system. J Am Diet Assoc. 2001;101;554-558,561.
- Brooks GA, Fahey TD, White TP. Exercise Physiology: Human Bioenergetics and Its Applications. Second Edition: Mayfield Publishing 1996.
- Geliebter A, Maher MM, Gerace L, Gutin B, Heymsfield SB, Hashim SA. Effects of strength and aerobic training on body composition., resting metabolic rate, and peak oxygen consumption in obese dieting subjects. Am J Clin Nutr. 1997;66(3):557-63.
- Horner NK, Patterson RE, Neuhouser ML, Lampe JW, Beresford SA, Prentice RL. Participant characteristics associated with errors in self-reported energy intake from the Women’s Health Initiative food-frequency questionnaire. Am J Clin Nutr. 2002;76(4):766-73.
- Johansson L, Solvoll K, Bjorneboe G, Drevon C. Under-and overreporting of energy intake related to weight status and lifestyle in a nationwide sample. Am J Clin Nutr. 1998;68:266-274.
- Lemmer JT, FM. Ivey, et al. Effect of strength training on resting metabolic rate and physical activity: age and gender comparisons. Med Sci Sports Exercise. 2001;33(4):532-41.
- Lichtman SW, Pisarska K, Berman ER, Testone M. Discrepancy between self-reported and actual caloric intake and exercise in obese subjects. N Engl J Med. 1992; 327:1893-1898.
- Walsh MC, Hunter GR, Sirikul B, Gower BA. Comparison of self-reported with objectively assessed energy expenditure in black and white women before and after weight loss. Am J Clin Nutr. 2004;79(6): 1013-9.
- Wescott, WL. What is the Fat-Burning Zone? Fitness Management, April 2005;32-33.