Free body fat index calculator and advice from Protéalpes' specialist pharmacists

What is IRC?

The Body Roundness Index (BRI) is a "new" body composition indicator proposed in ²⁰¹³¹. It combines height and waist circumference to better reflect the distribution of body fat, particularly abdominal visceral fat.

Potential advantages over BMI

1. Better health risk assessment: a recent ^study2 published in JAMA Network Open showed thatCKD was more effective than BMI in predicting mortality risk.
2. Taking visceral fat into account: CKD better reflects abdominal fat, an important risk factor for various diseases.
3. More precise for certain populations: IRC would be better suited to people with atypical morphologies, such as top-level athletes.
4. BMI, today's reference index, only takes into account weight and height, without distinguishing between muscle mass and fat mass.

Applications in medical research

Recent studies have shown associations between CKD and :

• The risk of cardiovascular disease
• The risk of colorectal cancer
• The risk of heart failure

Calculation and interpretation

The CRI is calculated using a complex mathematical formula incorporating waist circumference and height. Its interpretation generally requires the use of a specific calculator.
If the model wants to be more representative than BMI, the function used makes it a more complex calculation for the population:

How to interpret CRI values? Lack of scientific precision.

Unlike BMI, CRI is more directly linked to body shape, making it more relevant for certain health analyses, particularly those related to cardio-metabolic diseases.

However, as the calculation is relatively complicated and not "officially" standardized, there are some differences in the values presented between different studies, making it difficult to standardize target values and/or values to be avoided.

For example, following our analysis of the recent ^study2 that rekindled interest in this index, we note that the authors present a CRI value of 5 as the target value (4.5 to 5.5), least linked to risk factors, and that these risks are linked to the CRI value in a U-shape around this value of 5.
However, if we take the formula presented by Thomas et ^al1and ^others3 later, a CRI of 5 for a 175 cm man is linked to a waist circumference of over 100 cm (2XL), which seems completely inconsistent. It is possible that the authors of this study used a variant calculation, which is not specified. In any case, if the link between CKD and metabolic diseases is proven, the target value of an "ideal" CKD is lacking at the time of writing (August 2024).

Even more so, Maessen et ^al3 in their work take as their reference group (without risk factors) over 3,000 people, with an average CRI of 3.7 (+/- 1.2). We're a long way from the value of 5. For our example of a 175 cm tall man, a CRI of 3.7 corresponds to a waist circumference of 90 cm, vs. over 100 for a CRI of 5.

Without prejudging a potential error in one or other of these studies, these discrepancies clearly show thatCKD is an interesting index, but very complicated to standardize and use in public health, unlike BMI, which is not very specific, but very simple and comparable between different groups of people, and whose reference values are precisely well defined at international level.

Overall scientific opinion

Although, on paper, the CRI seems to offer certain advantages over the BMI, it still has its own limitations and requires further research to be fully validated and adopted into clinical practice. A precise framework is needed for target values, whether or not associated with risk factors.

The CRI seems to be an interesting indicator that could complement or replace the BMI in certain contexts, but many practitioners are very reluctant to use this index in their practice.

Indeed, as we have just seen, the CRI is far more complex to calculate than the BMI, to the point where the studies that refer to this index present results and values that are sometimes inconsistent and incomparable.

In conclusion, while a more precise association than BMI with metabolic and/or cardiovascular risk factors has been well documented for CKD, its widespread adoption will require more research and a clear simplification and/or standardization of its calculation. No, CRI will not soon replace BMI.

To tell the truth, it was a recent study in June 2024 that rekindled interest in the IRC, but this index has been around for over 10 years, and there are many others, more or less useful and complex.

Is IMM a better solution than IRC or IMC?

The Lean Mass Index (LMI) has certain advantages over the Body Mass Index (BMI) and the Body Depth Index (BDI), but is not necessarily a "better solution" in all cases. It is of interest in the sporting field, in order to monitor an athlete's progress in his or her physical preparation.

It should be remembered, however, that the CRI was developed primarily to assess obesity-related health risks in the general population, and not to assess the fitness of athletes.

Regarding BMI and its calculation, it differs from BMI in that it takes into account body composition rather than simply comparing weight to height. This enables a more accurate assessment of muscle mass, which is more useful for :

• Athletes and very muscular people
• Evaluating progress in a bodybuilding program

In conclusion, the BMI is not necessarily a better solution than the CRI or BMI in every case, but it does offer a different and complementary perspective. Its calculation is straightforward, but requires data that is sometimes difficult to obtain precisely: the percentage of body fat.

For top-level athletes, various body composition assessment methods are generally used to determine the percentage of body fat, such as skinfold measurement, two-photon X-ray absorptiometry (DEXA), or bioelectrical impedancemetry. It is then essential to follow up with the same tool used for the initial measurement of body fat.

The choice of the most appropriate index depends on the specific context and objectives of the assessment. An approach combining several indices could provide a more complete picture of an individual's health and body composition.

How to reduce waist circumference to improve CRI and limit health risks?

Reducing waist circumference, improving Body Circumference Index (BCI) and limiting health risks is a long-term process. It requires a comprehensive approach combining diet and exercise:

• Eat a varied and balanced diet, limiting processed foods, additives and sweeteners.
• Drink enough water.
• Get enough quality sleep.
• Avoid sugary industrial drinks not linked to post-exertion glycogen depletion.
• Practise regular sports sessions incorporating high- and low-intensity "cardio" exercises (running, skipping, HIIT...) as well as muscle-strengthening exercises (squats and squat jumps, burpees, planks, push-ups, pull-ups...).
• Avoid drastic diets and prefer a balanced, progressive, long-term approach, adapted to proteins (1.3/2 g/kg/d), carbohydrates (approximately 50% of total energy intake) and lipids (approximately 25 to 30% of total energy intake).
• Manage stress, which can influence abdominal weight gain.

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