indice massa corporea bmi pacifico obesita

The inhabitants of certain Pacific islands are among the most obese in the world, why? The limits of BMI

The Body Mass Index (in acronym BMI and in Italian Body Mass Index), invented by Adolphe Quetelet in the 19th century, it is a system for classifying body weight, adopted by the WHO in the 20th century for more immediate identification overweight And obesity. The Index presents however significant limitations and in this regard an emblematic case is that of some Pacific populationswhere beyond the 90% of adults, based on BMI, would be considered overweight or obese. However, this classification does not always reflect the real health condition of these people, underlining the urgency of more flexible, precise and culturally adaptable approaches. Let’s delve deeper into the question.

What is BMI, body mass index, and how is it calculated: the reference table

The BMIacronym for Body Mass Index and translated into Italian as Body Mass Indexwas developed by the Belgian mathematician Adolphe Quetelet in the 19th century (so much so that it was initially known as the “Quetelet Index”). Its aim was to measure the proportions of an average body in the European population. Only in Nocevento did the WHO adopt it as a tool to identify health states and weight categories such as overweight and obesity. However, the universal use of BMI has revealed several limitations, especially when applied to populations with different physical, lifestyle and genetic characteristics compared to Western populations.

BMI is obtained through a formula: divide the body weight in kilograms by the square of the height in meters:

BMI = weight (kg) / height2 (m)

The result is then compared with a stairs which classifies people into underweight (BMI less than 18.5), normal weight (18.5-24.9), overweight (25-29.9) e obesity (30 and above).

BMI table
Reference table for calculating the BMI (Body Mass Index)

The limits of BMI: the “Pacific paradox”

The body mass index is a simple and immediate tool, but it has numerous limitations: it does not consider body composition (ratio between fat mass and muscle mass), fat distribution and genetic differences between populations. For example, an athlete with a high muscle mass might be classified as “obese” despite having a normal body fat percentage, due to the high density of muscle mass compared to fat mass.

One of the most striking examples is what we could call the “Pacific paradox”. Someone Pacific Islands have always been at the top of the global ranking of countries with the highest average BMI, drawn up by the WHO, according to which more than 90% of the adult population of Nauru, Tonga and Samoa is classified as overweight or obese. For example:

  1. Nauru: About 61% of adults are obese.
  2. Tonga: About 48% of men and 70% of women are classified as obese.
  3. Samoa: Almost 60% of the adult population has a BMI above 30.

These rates are among the highest in the world, far exceeding those of many Western countries, which on average have obesity rates between 20% and 30%. Populations like those in the Pacific, however, unlike us Westerners, have one body genetically predisposed to develop greater muscle mass and robustnessmaking the use of BMI as the sole indicator of health partially inadequate.

A study of Tongan athletes, for example, showed that many of them are “obese” according to BMI, despite having low percentages of body fat. In this sense, genetics plays a fundamental role: Pacific populations seem to have a predisposition to conserve body fat more efficiently, a evolutionary adaptation to cope with long periods of food scarcity.

BMI in women
BMI map in women in 2016 (the darker the color, the higher the Index). Credits: Our World in Data

BMI in hand
Map of BMI in men in 2016 (the darker the color, the higher the Index). Credit: Our World in Data

The data partially supports the BMI

Although genetic characteristics offer a partial explanation for the high BMI in Pacific Islanders, other data supporting the validity of the Index cannot be ignored, e.g. the increase in obesity-related diseaseslike the type 2 diabetes and the cardiovascular diseases. In Tonga, for example, 34% of adults suffer from diabetes, a rate significantly higher than the global average. The cause of this increase in pathologies must be found in a complex one combination of historical, economic and cultural factors.

Before the arrival of Europeans, the traditional Pacific diet was rich in fish, tubers, fruits and vegetables. However, with colonization and globalizationthese eating habits have changed dramatically. Today, much of the islands depend on imported foodsOften low-cost hyper-processed foodssuch as canned meat and fish and sugary snacks. These foods, rich in calories but lacking in essential nutrients, have replaced traditional diets, thus favoring the onset of diseases linked to dysfunctional eating styles. Also the reduction ofphysical activitydue to urbanization and the mechanization of agricultural work, has had a negative impact. Currently, only 20-30% of adults in the Pacific Islands engage in sufficient physical activity to maintain optimal health, according to WHO data.

The response of international cooperation against obesity

To address the increase in obesity-related diseases, several international organizations have launched cooperation programs aimed at promotion of healthier lifestyles in the Pacific Islands. An example of these efforts is the program Healthy Islands, supported by WHO and UNICEF, which aims to promote a more balanced diet and one active lifestylewhile enhancing the local traditions. The idea behind these projects is to return to historical practices, such as growing local foods, while reducing dependence on imported and processed foods.

Despite good intentions, many of these programs have encountered several obstacles. Promoted diets, often based on foods that are expensive or not locally available, have achieved poor uptake. Furthermore, limited health infrastructure and economic difficulties make it difficult for many inhabitants to adopt a healthy lifestyle. The communication of these programs, often not adequately adapted to cultural specificities, meant that many inhabitants did not understand or accept the suggested changes. The idea, for example, of a robust body as a symbol of prosperity and health is ingrained in many Pacific cultures, making promoting weight loss as a wellness goal complicated.

These scenarios make clear the need to adopt approaches that combine local wisdom and global resources, enabling sustainable and culturally sensitive changesto effectively address food challenges in the Pacific.