Dr Pierre Decazes

Towards a new definition of obesity

drdecazes — Wed, 12 Feb 2025 16:24:19 +0000

The body mass index is outdated

We saw in a previous article that, while the World Health Organization (WHO) uses the Body Mass Index (BMI) to define obesity when the BMI exceeds 30 kg/m2, this parameter can be misleading, as some people above this threshold may have normal body fat (such as athletes with high muscle mass) and, conversely, others with a BMI below this threshold may have significant body fat.

On the other hand, many people with excess adipose tissue show no signs of disease.

So, while BMI is useful at the population level, its ability to predict health status at the individual level is more limited.

Anthropometry is now preferred

Rather than using BMI alone to define obesity, anthropometric measurements of body fat are now used to diagnose obesity [1].

These measurements can be indirect (such as waist circumference, which reflects visceral fat mass within the abdominal cavity) or direct (such as biphotonic absorptiometry, which uses X-rays to measure the fat compartment).

Thus, for Caucasians, the diagnosis of obesity can now be made when a BMI greater than 30 kg/m2 is combined with a waist circumference ≥ 102 cm for men and ≥ 88 cm for women.

If the BMI is less than 30 kg/m2 or is unknown, the diagnosis of obesity can still be made by combining two of the following three anthropometric parameters:

Waist circumference ≥ 102 cm for men and ≥ 88 cm for women (for Caucasians)
Waist/hip circumference ratio > 0.90 for men and > 0.85 for women
Waist/height ratio > 0.50 for both men and women.

Finally, independently of BMI and other simple clinical measurements, the diagnosis can be made by direct measurement of body fat (DEXA or CT scan, for example).

Thanks to these anthropometric measurements, muscular people with a high BMI but low body fat will not be wrongly diagnosed as obese.

Pre-clinical or clinical obesity?

A diagnosis of obesity (excess body fat) does not, however, imply disease.

Indeed, while obesity is a risk factor for the development of diseases (cardiovascular, type 2 diabetes, etc.), not all obese people suffer from symptoms or illnesses linked to their obesity. They may even experience no discomfort in their daily activities. In this case, we speak of preclinical obesity.

If, on the other hand, there are limitations to daily activities, or symptoms or illnesses linked to obesity, we speak of clinical obesity. People suffering from clinical obesity have a variety of impairments, including :

Shortness of breath due to the effects of obesity on the heart or lungs,
Knee or hip pain accompanied by joint stiffness and reduced range of motion.
A range of metabolic abnormalities (diabetes, etc.)
Dysfunction of other organs, including the kidneys, upper respiratory tract, nervous, urinary and reproductive systems.

It is important to ensure, however, that the symptoms/signs of organ dysfunction and/or reduced daily activities are consequences of obesity, if the diagnosis of clinical obesity is to be retained.

What about you?

Modify the values below to customize the article:

References

1. Rubino F, Cummings DE, Eckel RH, Cohen RV, Wilding JPH, Brown WA, et al. Definition and diagnostic criteria of clinical obesity. The Lancet Diabetes & Endocrinology. janv 2025

The post Towards a new definition of obesity appeared first on Dr Pierre Decazes.

Choose your ideal weight

drdecazes — Thu, 09 Jan 2025 21:37:59 +0000

Modify the values below to personalize the article:

What is the ideal weight?

Ideal weight refers to a body weight considered optimal for an individual’s health, based on various criteria such as height, age, sex, muscle mass, body composition, and activities. Ideal weight also depends on personal aspirations and what one aims to achieve with their body. For instance, a study conducted by Sedeaud et al. analyzed the BMI of athletes based on running events and showed that marathon runners tend to have a lower body mass compared to 100-meter sprinters, even at the same height. [1]

Mathematical formulas: variable and limited results

Ideal weight formulas aim to estimate a theoretical weight based on parameters such as height, sex, age, or body type. However, their results often vary depending on the approach and have certain limitations. For example, the Broca formula, simple and easy to remember, relies solely on height. It is often cited as the basis for other formulas, even though its results can sometimes be too approximate.

Ideal weight (kg) = Height (cm) – 100

Example: For a person measuring 170 cm, the ideal weight would be 70 kg. The Lorentz formula improves upon Broca’s by introducing an additional adjustment based on sex. It is particularly popular in countries using the metric system.

- For men:
  Ideal weight (kg) = Height (cm) – 100 – (Height (cm) – 150) ÷ 4
- For women:
  Ideal weight (kg) = Height (cm) – 100 – (Height (cm) – 150) ÷ 2.5

Example: A man measuring 170 cm would have an ideal weight of 65 kg. A woman measuring 170 cm would have an ideal weight of 62 kg. As for the Devine formula, originally developed to adjust medical dosages, it is expressed in inches and remains popular in English-speaking countries.

For men:
Ideal weight (kg) = 50 [kg] + 2.3 × {Height (in inches) – 60}
For women:
Ideal weight (kg) = 45.5 [kg] + 2.3 × {Height (in inches) – 60}

To convert centimeters to inches: 1 cm = 0.3937 inches. Example: A woman measuring 170 cm (equivalent to 66.93 inches) would have an ideal weight of 61 kg.

Ideal weight according to the Broca, Lorentz, and Devine formulas:

Broca Formula: Calculating...
Lorentz Formula: Calculating...
Devine Formula: Calculating...

The Perrault formula introduces age as a parameter to reflect body changes associated with aging, resulting in an ideal weight that increases with age.

Ideal weight (kg) = Height (cm) – 100 + (Age (years) ÷ 10 × 0.9)

Example: A person measuring 170 cm and aged 30 years would have an ideal weight of 72.7 kg, while at 70 years old, their ideal weight would be 76.3 kg.

Ideal weight according to the Perrault formula: Calculating...

Finally, the Creff formula goes a step further by taking into account an individual’s body type (normal, large, or slender-gracile).

Normal body type:
Ideal weight (kg) = Height (cm) – 100 + (Age (years) ÷ 10 × 0.9)
Large body type:
Ideal weight (kg) = Height (cm) – 100 + (Age (years) ÷ 10 × 0.9 × 1.1)
Slender-gracile body type:
Ideal weight (kg) = Height (cm) – 100 + (Age (years) ÷ 10 × 0.9 × 0.9)

Example: A person measuring 170 cm, aged 30 years, and with a “gracile” body type would have an ideal weight of 72.4 kg.

Ideal weight according to Creff formulas:

Normal morphology: Calculating...
Large morphology: Calculating...
Gracile morphology: Calculating...

Towards body mass index (BMI)

Mathematical formulas, useful but imperfect, have been supplanted by the Body Mass Index (BMI), which today assesses corpulence by comparing height and weight to standardized thresholds, rather than calculating an “ideal” weight. BMI calculation:

BMI (kg/m²) = Weight (kg) ÷ Height² (m²)

BMI is a standardized measurement recognized by the World Health Organization (WHO) for determining health risks. It is calculated by dividing weight (in kilograms) by the square of height (in meters). The WHO has defined categories for interpreting BMI: a BMI below 18.5 is considered underweight, between 18.5 and 24.9 normal weight, between 25 and 29.9 overweight, and 30 or more obese (with varying degrees). These thresholds raise awareness of health risks, such as malnutrition for low BMIs, or chronic diseases like diabetes and cardiovascular disease for high BMIs.

Legend:

Underweight

Normal weight

Overweight

Mild obesity

Moderate obesity

Severe obesity

Selected point

The BMI limits set by the WHO are highly standardized, which means that individual variability cannot be taken into account. For example, the natural tendency of BMI to be higher in men than in women is not incorporated into these thresholds. What’s more, these categories do not always reflect a precise correlation with survival rates, as demonstrated by the curve of mortality risk as a function of BMI, derived from recent data from the vast American NHANES cohort [2]. Furthermore, mortality is generally higher for low BMIs, often associated with insufficient muscle mass, and for high BMIs, where excessive accumulation of fat mass can increase the risk of cardiovascular and metabolic diseases. This analysis underlines the limitations of the standardized approach, and highlights the importance of contextualizing BMI interpretations according to individual characteristics and study populations.

In this way, the risk of death can be further personalized by taking into account gender, age and BMI.

However, while BMI is an indicator of corpulence, it does not distinguish between muscle mass and fat mass. So, for athletes or very muscular people, BMI may not be a reliable indicator of health risk.

Summary

You’ve seen various formulas for estimating ideal weight, all of which take more or less information as input to the calculation.

This approach has now been replaced by BMI. According to the WHO, a normal BMI is between 20 and 25 kg/m2.

This definition has the advantage of simplicity, but if you want the “ideal weight” to reflect a mortality risk, larger intervals can be used, particularly according to recent cohorts.

References

1. Sedeaud A, Marc A, Marck A, Dor F, Schipman J, Dorsey M, et al. BMI, a Performance Parameter for Speed Improvement. PLOS ONE. 25 févr 2014;9(2):e90183.

2. Visaria A, Setoguchi S. Body mass index and all-cause mortality in a 21st century U.S. population: A National Health Interview Survey analysis. PLOS ONE. 5 juill 2023;18(7):e0287218.

The post Choose your ideal weight appeared first on Dr Pierre Decazes.

What is sarcopenia?

drdecazes — Mon, 16 Dec 2024 17:51:23 +0000

Sarcopenia: an under-recognized disease despite its major clinical implications

Sarcopenia, characterized by age-related loss of muscle mass and reduced muscle strength and function, is associated with increased risk of falls, disability and mortality.

However, this condition remains poorly recognized in clinical practice, and no pharmacological treatment is currently available. Despite the existence of an ICD10-CM code, sarcopenia lacks a comprehensive and universally accepted definition, limiting its systematic use in medical practice.

A key challenge for better management of this pathology remains the establishment of a standardized, operational definition.

Development of a global definition

Until now, there has been no universal definition of sarcopenia. The Global Sarcopenia Leadership Initiative (GLIS) was created to solve this problem. 107 professionals from 29 countries took part in a Delphi study to establish a consensus, with publication of their initial findings in 2024 [1].

Key points of the definition

Essential components: Sarcopenia is characterized by a combination of reduced muscle mass, reduced muscle strength and, potentially, reduced specific muscle strength (strength standardized by muscle size).
Health consequences: This disease is associated with impaired physical performance, mobility limitations, increased risk of falls, fractures, hospitalizations, nursing home admissions, and reduced quality of life.
Reversible disease: Sarcopenia is considered a treatable condition, paving the way for nutritional, physical and pharmacological interventions.

Challenges and next steps:

The transition to a practical definition of sarcopenia is underway. This involves determining how to effectively measure muscle mass and strength, as well as specific muscle force, while taking into account measurement validity, clinical feasibility and normative data across populations.

Multidisciplinary working groups will collaborate to define harmonized criteria, comparable to advances made in the fields of osteopenia and osteoporosis.

A global pratical definition will enable :

Harmonization of research on an international scale.
Identification of sufferers for better screening.
Development and evaluation of targeted therapeutic interventions.

Conclusion:

This new conceptual definition marks a major advance in the understanding and management of sarcopenia. By bringing together experts from diverse backgrounds, GLIS is paving the way for essential clinical and scientific innovations to meet this major challenge of aging.

Référence

1: Kirk B, Cawthon PM, Arai H, Ávila-Funes JA, Barazzoni R, Bhasin S, Binder EF, Bruyere O, Cederholm T, Chen LK, Cooper C, Duque G, Fielding RA, Guralnik J, Kiel DP, Landi F, Reginster JY, Sayer AA, Visser M, von Haehling S, Woo J, Cruz- Jentoft AJ; Global Leadership Initiative in Sarcopenia (GLIS) group. The Conceptual Definition of Sarcopenia: Delphi Consensus from the Global Leadership Initiative in Sarcopenia (GLIS). Age Ageing. 2024 Mar 1;53(3):afae052. doi: 10.1093/ageing/afae052.

The post What is sarcopenia? appeared first on Dr Pierre Decazes.

(When) will you become sarcopenic?

drdecazes — Tue, 10 Dec 2024 14:30:05 +0000

Sex :

Weight (kg) :

Height (cm) :

Age (years) :

Ethnicity :

Estimated annual muscle decline from age 40 onwards:

Waist circumference (cm) (more precise but optional) :

Sarcopenia: What is it and how can it be prevented?

Sarcopenia is a little-known term that affects a significant proportion of the aging population. It refers to a progressive loss of muscle mass, strength and function, generally associated with advancing age. This condition has consequences for mobility, autonomy and overall quality of life. In particular, it increases the risk of falls and fractures.

Causes of sarcopenia

Sarcopenia is not a fatality of aging, but the result of a combination of factors. Physical inactivity, insufficient protein in the diet, and hormonal changes (such as a drop in testosterone in men and estrogen in women) can be the main causes. As the body ages, it also becomes more difficult to repair and maintain muscle mass.

Are you at risk?

The diagnosis of sarcopenia takes into account muscle mass and function. It is not, however, a sudden onset disease, but a progressive one linked to muscle loss. Loss of muscle mass occurs as early as middle age around 40 (∼1%/year) and, in the most severe cases, can reach ∼50% in the 8th or 9th decade of life [1]. Below you’ll find a calculator to estimate your muscle mass [2] and the potential age of onset of low muscle mass (11 kg/m2 for men and 9 kg/m2 for women) [3]

About calculations

The calculator uses formulas developed in a study investigating the relationships between height, age, mass, waist circumference and muscle mass [2]. This study was based on a large database of 12,330 individuals from the National Health and Nutrition Survey (NHANES). Skeletal muscle mass was measured by dual-photon absorptiometry (DXA), and an MRI-derived predictive equation was used to calculate total muscle mass from lean limb mass (arms and legs). For low muscle mass thresholds, these were determined from a base of 1293 patients with muscle mass measurement by bioimpedancemetry (BIA) and comparison to handshake strength.

References

1. Volpi E, Nazemi R, Fujita S. Muscle tissue changes with aging. Curr Opin Clin Nutr Metab Care. juill 2004;7(4):405‑10.

2. Heymsfield SB, Stanley A, Pietrobelli A, Heo M. Simple Skeletal Muscle Mass Estimation Formulas: What We Can Learn From Them. Front Endocrinol, 2020

3. Bahat G, Tufan A, Kilic C, Aydın T, Akpinar TS, Kose M, et al. Cut-off points for height, weight and body mass index adjusted bioimpedance analysis measurements of muscle mass with use of different threshold definitions. The Aging Male. 4 déc 2020;23(5):382‑7.

The post (When) will you become sarcopenic? appeared first on Dr Pierre Decazes.

Unexpected Side Effects of GLP-1 Analogues?

drdecazes — Tue, 10 Dec 2024 14:23:00 +0000

Today, I was reflecting on GLP-1 agonist analogues (Glucagon-Like Peptide).

Doesn’t ring a bell? Sure it does! It’s that new class of drugs (like semaglutide – Wegovy – Ozempic) that create a prolonged feeling of satiety. These medications help people eat less, leading to weight loss.

Initially developed for diabetes management, these treatments are increasingly being promoted as obesity therapies. More importantly, they show promise in preventing diseases linked to obesity.

One might think that humanity has finally found a solution to a problem that never existed in nature. Nutritional energy abundance, after all, is a “modern” invention. Over the course of evolution, our bodies never needed to develop defense mechanisms against energy storage in fat.

But here’s the thing: I’m not quick to believe in “miracle” drugs and prefer to dig into potential side effects.

One potential “side effect,” a kind of unexpected “double impact” effect (a long-term secondary effect), is the decrease in both the quantity and quality of muscle mass during weight loss induced by these treatments. In fact, people naturally lose about 0.8% of muscle mass per year (8% per decade) between the ages of 40 and 70. With these drugs, muscle loss (as indicated by the reduction in lean body mass) accounts for 25 to 39% of the total weight lost! [1]

While losing fat may have its benefits, no good comes from muscle wasting.

So, if obesity is the epidemic of the century, potentially curable with these treatments, sarcopenia (the decline in muscle quantity and quality, particularly in older adults) might well become the epidemic of the next century.

1. Prado CM, Phillips SM, Gonzalez MC, Heymsfield SB. Muscle matters: the effects of medically induced weight loss on skeletal muscle. The Lancet Diabetes & Endocrinology. nov 2024;12(11):785‑7.

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