Overweight? Relax, it  Doesn’t Equal Early Death Reveals Study

Being overweight may not be good for your health but not so bad as to cause you an early death. This is evident in a new large U.S. study that classifies individuals into overweight, but not obese, who do not have the risk of early dying¹. 

The study was published in the online journal Plos One and highlights that being overweight does not risk you dying earlier. What made researchers conclude this, how was this 20-year-long study conducted? Let’s find out in this article.

Inconsistent Findings: Previous Studies on Weight, related death

There’s no doubt that being overweight, but not obese, is bad for health. However, it is not clear at what point overweight the health risk begins. There are several previous large and popular U.S. studies that have linked the overweight with a lower risk of death. But, according to the author of the present research paper, the findings of these studies are inconsistent. 

Some show lower risk and few other claims significantly higher mortality risk. These studies also focused on a specific race (non-Hispanic White men and women). Contrary to this, the present U.S. population has a diverse race. There are few recent studies covering the recent population, however, their sample size is considerably small.

In this recent study, the team of U.S based researchers were curious to bridge this gap. They also aimed to analyse across racial and gender subgroups.

Utilizing data from National Health Interview Survey (NHIS)

The research team utilised data from the National Health Interview Survey (NHIS). It is a survey of the noninstitutionalized U.S. population in which NHIS collects data through household interviews. The survey tracks health status and is collecting data from the last 20 years. 

For the present study, the researchers included non-pregnant adults aged 20 years and older who had recorded BMI information. BMI or Body Mass Index gives us an idea of whether our body weight is appropriate for our height. 

It tells you whether your weight is underweight, ideal, overweight or obese. If you know your height and body weight you can easily calculate your BMI using this online BMI calculator. The commonly accepted BMI score range for overweight is 25 to 29.9.

For the present study purpose, the research team classified BMI into 9 categories: <18.5, 18.5–19.9, 20.0–22.4, 22.5–24.9, 25–27.4, 27.5–29.9, 30.0–34.9, 35.0–39.9, ≥40 kg/m2. A BMI score between 22.5 to 29.9 is categorised as overweight. It is this range in which the team was interested.

Examining All-Cause Mortality: Linking NHIS Data to the National Death Index

To find out whether the risk of death increases, remains the same or decreases within this overweight range, the researchers needed data related to all-cause mortality. This data for All-cause death was obtained from the U.S. National Death Index (NDI). The doctors linked the NHIS data from 1999 to 2018 to the NDI by using unique patient identifiers. 

They were also interested to find how other factors affect death risk in overweights, these factors include:

1. Demographic characteristics (age, gender, race/ethnicity), 
2. Socio-behavioural factors (education, marital status, physical activity, smoking status, alcohol consumption, insurance coverage, region of residence, citizenship status), 
3. Comorbidities (self-reported history of cardiovascular disease, non-skin cancer or melanoma, chronic obstructive pulmonary disease [COPD], current asthma, liver disease, kidney disease, diabetes, or functional limitations), and 
4. Healthcare utilization factors (doctor’s visit and mental health visit in the past 12 months). Details about the categorization of covariates can be found in the supplement (Extended Supplementary Methods).

For this doctors collected data from other studies that included BMI and mortality.

Surprising Results: Overweight Not Linked to Risk of Early Death

The result of the study gives evidence that being overweight is not bad for your health after all. This long 20-year study has over 550,000 U.S. adult participants and the result was surprising, the study revealed that the risks of all-cause mortality were similar across all the 9 ranges of BMI values, including the overweight range of 22.5 to 29.9 kg/m2. 

This clearly indicates that being overweight doesn’t have a link to the risk of early death. 

Interestingly, research also revealed that overweight older adults of age more than 65 had a lesser risk of dying, while younger adults (aged less than 65 years) had an increased mortality risk. Also, among younger adults, a BMI of 27.5-29.9 was associated with nearly a 20% higher mortality risk, consistent with findings from the pooled analysis of the National Cancer Cohort Consortium.

Survival Advantages, Metabolic Health in Overweight Individuals could be possible cause

The author of the paper indicates some possible causes of this BMI and less risk of dying in overweight individuals. Overweight individuals may have survival advantages in adverse circumstances, and those without diseases may be metabolically healthy with a more favourable body composition. 

Additionally, lean individuals who develop diseases may have more aggressive or treatment-resistant conditions, while overweight or obese individuals may be able to manage or reverse disease with weight loss strategies. 

BMI Alone is Insufficient: Need for Comprehensive Assessment of Body Composition

The findings of this large study suggest that BMI in the overweight range is generally not associated with an increased risk of all-cause mortality. This clearly highlights that BMI alone may be insufficient in capturing high-risk adiposity, and factors such as waist circumference and weight change over time can modify the BMI-mortality association. 

The author suggests the need for future studies, considering additional measures of body composition, and comprehensive assessment of the impact of weight on psychological and morbidity outcomes to better understand the relationship between BMI and mortality.

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