Calorie Requirement Question & Answer

Disappointed Visitor

I just finished my sports nutritionist. While adequate with knowledge, her recommendations have all been shoved in trash because she used your Target Weight / Body Composition calculator that is very inaccurate.

Body fat % is off by at least 3% (per biometric measurements) and the supposed target weight would leave me overweight per current guidelines. This led her to overestimate my caloric needs by nearly 1000 calories per day. Wow. What’s even more interesting is that other software she used to calculate my caloric need targets my ideal body weight at 20 pounds less than your software and is in line with currently acceptable body fat levels and BMI.

This is extremely concerning. I can’t cannot recommend this software or her, because of this blazingly incorrect assessment. How is is that your software can be so inaccurate and discordant with current guidelines?

Target Weight.jpgThank you for sharing your concern. I am sorry to hear about you ordeal.

First, the target weight/body composition calculator is nothing more than a calculator to show resultant values under specific target changes to fat and lean weight. This calculator makes no recommendations for your ideal body weight. The resultant Target Weight is a result of your current stats and whatever value your nutritionist entered into Target Percent Fat. I assume she did not attempt to predict your lean weight change. Similar to a financial calculator, the actual values will likely differ from the initial projected values since it can be most challenging even for a very experienced exercise and nutrition expert to accurately predict gains or losses in both fat and lean body mass. The bottom line is that this calculator makes no recommendations as you appear to believe.

Second, the techniques and formulas used in our calculators are not our own and are widely used in this field since they are found in many fitness testing and nutrition assessment textbooks. You’ll find the references below each calculator. Exercise professionals and nutritionists have been using these techniques and formulas for many decades.

However, there remains multiple ways to assess body composition and caloric needs. It is important that the fitness professional appropriately chooses fitness tests that best suits the client and consistently uses the same techniques to detect changes. The calculators provided rely on the ability of the fitness/health professional to use the relevant tools and complete the assessment properly.

In the case of the body composition calculator, improper instruction or training on how to take skinfold measurements can lead to inaccurate results. It requires hundreds, if not thousands, of administered skin fold tests for a practitioner to obtain the most accurate and consistent measurements. Even when performed correctly according to recommended guidelines, the validity of the skin fold test has a +/- 3% SEE as compared to hydrostatic weighing. There is also slight variability in finding measurements within the skin fold procedure itself. Techniques such as measuring skinfold  are meant to predict body composition, not provide an exact measurement. However, once a baseline value is established the same test can be used to detect changes.

It is common for two different tests which indirectly measure a variable to result in varying values despite being designed to estimate the same component. This means estimating body comp by skinfold versus bioelectrical impedance will not likely yield the exact same results. All body composition tests, or fitness tests for that matter, have their strengths and weaknesses, including the ‘gold standard’ body composition test by means of hydrostatic (underwater) weighing. Interestingly, certain studies have revealed NFL players being measured at negative body fat percentage as this test cannot account for the greater bone density of these athletes.

In a similar way, when using BMI to determine weight classification as per current guidelines (as you cite), the results can be misleading (See BMI Calculator). BMI have value in epidemiological studies for assessing the general population, but is not as reliable for individual body composition assessment, especially for athletes. In fact, many athletes have shown to be overweight/obese because of their greater lean body mass which cannot be differentiated from fat mass, since BMI is calculated using only height and weight. It is necessary to consider body composition when determining the classification of a healthy weight for an individual.

The ExRx.net Estimated Calorie requirement Calculator defaults to the widely used Harris Benedict Equation, which takes into account the height and weight of the individual. An alternative formula also provided which takes body fat percentage into account. These are commonly used formulas from energy metabolism studies and use data from average individuals, not necessarily athletes. Again, they are not our proprietary formulas and they will yield slightly different caloric requirements depending on the formula chosen. For example, individuals with higher lean body mass that opt for the equation accounting for body fat percentage may get results that suggest greater caloric needs. It is at the discretion of the practitioner to choose which formulas are best for calculating the caloric requirements of the client.

In any case, these calculations are based on averages and can be off by as much as 20-30 percent in normal, young, healthy people; even more in special populations. Calorie calculators can still be very helpful but it’s important to be aware of their limitations. The results are meant to estimate a rough starting point, but not to provide a definitive calculation, even for the alternative one you ended up using.

Calculating estimated caloric intake must also take into account other factors such as daily energy expenditure and activity level, which can easily be overestimated leading to a subsequent overestimation of caloric needs. For example, many people forget to take an account rest periods during weight training and intermittent sports drills and end up grossly overestimating caloric expenditures if they tally that activity under 'Heavy' activity. In most cases, we suggest weight training to be tallied under the 'Moderate' activity field, but this may very somewhat depending upon the intensity and rest periods.

Another common source of over estimation of activity level is failing to take in account of activities that are not performed every day. It is important correct for number of days per week if particular activity levels are not performed daily. For example, if you perform one hour of sports training 5 days per week, you should only report an average of 0.71 hours per week (5 days/7 days x1 hour) from that particular activity. If you accurately reported one hour per day from this single activity, you would be significantly be overestimating your caloric requirements.

When performed by a skilled and experienced professional, these tools can be useful in estimating body composition and determining caloric needs. The Target Weight Calculator is essentially a basic math calculator and makes no recommendations. BMI does not take into account lean body weight thereby classifying some athletes as overweight. Inevitably, there will always be variations and inaccuracies in all body composition tests since they typically do not directly measure body composition. Likewise, there will also be inaccuracies and variations in estimating caloric needs depending on a number of factors. It is up to the exercise professional to determine which assessments and formulas are most accurate and appropriate for each individual clients. And finally, it is critical to be able to accurately perform the tests and in the case of determining caloric requirements, to accurately determine and enter the average time spent at each activity level.

I’ll include this on our site so others that may be faced with a similar situation can avoid confusion and understand why these discrepancies may occur. Thanks again for your comments.

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