Study Questions Ideal BMI: Underweight Linked to Higher Mortality
A Danish study of 85,761 people suggests being underweight significantly increases mortality risk, while moderate overweight shows no excess.
English · Original discussion in Spanish · Published
85,761 People and 7,555 Deaths: The Ideal Weight Falls Short
What if the weight that medicine has promoted as ideal for decades isn't the one associated with the lowest mortality? A Danish study involving 85,761 individuals, mostly women (81.4%) with an average age of 66.4 years, concludes that those in the lower end of the 'normal' range die more often than those who are overweight. Over five years of trinc-up, 7,555 deaths were recorded. The reference group had a BMI between 22.5 and less than 25.
The numbers are unsettling. Individuals who were underweight had 2.73 times higher probabilities of dying compared to the reference group. A BMI between 18.5 and less than 20 doubled the risk; another between 20 and less than 22.5, well within the 'healthy' range, increased it by 27%. At the other end, a BMI over 40 multiplied the risk of death by 2.1. Overweight (25 to less than 30) and mild obesity (30 to less than 35) showed no excess mortality, with a clear increase starting from 35, showing a 23% rise. The conclusion is as simple as it is uncomfortable: thinness doesn't always work in your favor.
Why is a Low BMI Associated with More Deaths?
Dr. Sigrid Bjerge Gribsholt from the Steno Diabetes Center Aarhus urges caution. The data comes from individuals who underwent examinations for health reasons, so reverse causality cannot be ruled out: some participants may have lost weight due to an underlying illness, in which case the illness, not the weight, is the cause of death. She adds a second possibility—that participants with higher BMIs and older age might possess protective traits that distort the picture—and reminds us that being underweight is linked to malnutrition, weakened immune systems, and nutritional deficiencies.
BMI Doesn't Distinguish Muscle from Fat
This is the most frequently mentioned point: the Body Mass Index does not differentiate between muscle mass and adipose tissue. An athlete or bodybuilder might have a BMI indicating overweight without an ounce of extra fat; a thin person with low muscle mass might have an impeccable BMI and still be at risk. To accurately measure body fat, the DEXA scanner is proposed, which is more stable than bioimpedance, which varies with body water and time of day. The home rule summarizing the issue: if you can pinch fat on your belly, you have excess; if there's nothing to grab, there's no fat to lose. And the nuance many emphasize: what erodes the body isn't weight, but sarcopenia, the loss of muscle.
The Village Grandparents Who Lived Past 90
Against statistics, life. Village grandparents and uncles, 'chubby,' who ate bread with cheese for breakfast, had their shot of brandy at noon, and ate turnip stew with pork cracklings; one lived to 97 with sky-high cholesterol and a nagging doctor. The common factor noted isn't the scale, but physical labor: gardening, hoeing, and working in the fields well into old age. Observation also works in reverse: it's argued that most active individuals over 75 are thin or very thin. And a home experiment is proposed: carrying 15 kilos in a backpack all day to instantly understand the weight of one's own body.
From the Overton Window to the Price of Flour
The headline has economic implications. With fresh foods becoming more expensive and carbohydrates cheap, some interpretations view the study as a way to normalize being overweight: lower future healthcare costs, unfunded pensions, a captive market for drugs and low-calorie products. It's important to separate the data from the theory. Conspiracy theories suggesting a deliberate campaign to make the population fat and then sell them the solution have no backing in the study or available data. What does change, if the 'healthy' range widens, is the framework of public conversation.
At its core lies an old question: if moderate overweight doesn't shorten life, why is it still treated as a death sentence? The 'fat but fit'—metabolically healthy—individual even appears in the Danish study, which simultaneously reminds us that obesity alters metabolism, weakens the immune system, and is associated with type 2 diabetes, cardiovascular diseases, and up to 15 types of cancer. No one emerges unscathed from a well-chosen statistic.
Let everyone decide what they have for dinner and how much their backpack weighs. The data, for now, hasn't made anyone fatter.
What if the weight that medicine has promoted as ideal for decades isn't the one associated with the lowest mortality? A Danish study involving 85,761 individuals, mostly women (81.4%) with an average age of 66.4 years, concludes that those in the lower end of the 'normal' range die more often than those who are overweight. Over five years of trinc-up, 7,555 deaths were recorded. The reference group had a BMI between 22.5 and less than 25.
The numbers are unsettling. Individuals who were underweight had 2.73 times higher probabilities of dying compared to the reference group. A BMI between 18.5 and less than 20 doubled the risk; another between 20 and less than 22.5, well within the 'healthy' range, increased it by 27%. At the other end, a BMI over 40 multiplied the risk of death by 2.1. Overweight (25 to less than 30) and mild obesity (30 to less than 35) showed no excess mortality, with a clear increase starting from 35, showing a 23% rise. The conclusion is as simple as it is uncomfortable: thinness doesn't always work in your favor.
Why is a Low BMI Associated with More Deaths?
Dr. Sigrid Bjerge Gribsholt from the Steno Diabetes Center Aarhus urges caution. The data comes from individuals who underwent examinations for health reasons, so reverse causality cannot be ruled out: some participants may have lost weight due to an underlying illness, in which case the illness, not the weight, is the cause of death. She adds a second possibility—that participants with higher BMIs and older age might possess protective traits that distort the picture—and reminds us that being underweight is linked to malnutrition, weakened immune systems, and nutritional deficiencies.
BMI Doesn't Distinguish Muscle from Fat
This is the most frequently mentioned point: the Body Mass Index does not differentiate between muscle mass and adipose tissue. An athlete or bodybuilder might have a BMI indicating overweight without an ounce of extra fat; a thin person with low muscle mass might have an impeccable BMI and still be at risk. To accurately measure body fat, the DEXA scanner is proposed, which is more stable than bioimpedance, which varies with body water and time of day. The home rule summarizing the issue: if you can pinch fat on your belly, you have excess; if there's nothing to grab, there's no fat to lose. And the nuance many emphasize: what erodes the body isn't weight, but sarcopenia, the loss of muscle.
The Village Grandparents Who Lived Past 90
Against statistics, life. Village grandparents and uncles, 'chubby,' who ate bread with cheese for breakfast, had their shot of brandy at noon, and ate turnip stew with pork cracklings; one lived to 97 with sky-high cholesterol and a nagging doctor. The common factor noted isn't the scale, but physical labor: gardening, hoeing, and working in the fields well into old age. Observation also works in reverse: it's argued that most active individuals over 75 are thin or very thin. And a home experiment is proposed: carrying 15 kilos in a backpack all day to instantly understand the weight of one's own body.
From the Overton Window to the Price of Flour
The headline has economic implications. With fresh foods becoming more expensive and carbohydrates cheap, some interpretations view the study as a way to normalize being overweight: lower future healthcare costs, unfunded pensions, a captive market for drugs and low-calorie products. It's important to separate the data from the theory. Conspiracy theories suggesting a deliberate campaign to make the population fat and then sell them the solution have no backing in the study or available data. What does change, if the 'healthy' range widens, is the framework of public conversation.
At its core lies an old question: if moderate overweight doesn't shorten life, why is it still treated as a death sentence? The 'fat but fit'—metabolically healthy—individual even appears in the Danish study, which simultaneously reminds us that obesity alters metabolism, weakens the immune system, and is associated with type 2 diabetes, cardiovascular diseases, and up to 15 types of cancer. No one emerges unscathed from a well-chosen statistic.
Let everyone decide what they have for dinner and how much their backpack weighs. The data, for now, hasn't made anyone fatter.
Summary of a discussion on Burbuja.info - Foro de economía, actualidad y política., translated from Spanish and reviewed before publication. Read the full discussion (216 replies).
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