The Obesity Paradox - Can Extra Weight Be Beneficial?
The “obesity paradox” is a medical hypothesis which subscribes to the belief that while obesity is a condition associated with an increased risk of hypertension, cardiovascular disease, cancer, diabetes, depression and all-cause mortality, it may exert some protective measures against chronic disease in certain groups of people, such as the elderly.
The idea of an “obesity paradox” first surfaced in 2002, when a study noted that individuals with higher body mass indices (BMI) had were less likely to die from cardiovascular-related disorders than those of normal weight and a healthy BMI. 
Related - Is Obesity Really That Dangerous?
Since its debut over 15 years ago, the hypothesis has been the subject of vehement debate and controversy. And, in 2018, a pair of studies provided strong evidence to nullify the obesity paradox hypothesis.
The first study, published in JAMA Cardiology, found that the obese live shorter lives, and they also have a higher percentage of life with cardiovascular disease.  Researchers analyzed data from 190,672 in-person examinations across 10 cohorts with an aggregate of 3.2 million years of follow-up. At the beginning of the study, all subjects were free of cardiovascular disease.
At the end of the study, researchers documented that normal-weight middle-aged men lived an average of 1.9 years longer than obese men and six years longer than morbidly obese. Additionally, obese middle-aged men (ages 40-59) had a 67% greater chance of having a stroke, heart attack, heart failure, or cardiovascular-related death than normal men. FYI, obese women had an 85% higher chance of cardiovascular-related issue than normal weight middle-aged women. 
The other notable study that provided evidence to counter the notion of obesity being “protective” comes from the European Heart Journal.  This cohort study involved nearly 300,000 people and found that an individual’s risk of cardiovascular complications increases as BMI rises above 22-23. Additionally, the authors also noted that risk of cardiovascular disorders steadily rises the more fat an individual carries around their waist. 
Specifically, researchers observed that CVD risk increased by 10% in men and 16% in women for every 11.4cm and 12.6cm increase in waist circumference for men and women, respectively. 
On publication of the findings, one of the study’s authors, Dr Stamatina Iliodromiti, stated:
“Any public misconception of a potential 'protective' effect of fat on heart and stroke risks should be challenged." 
The researchers also gave some insight into why some may believe the idea of an obesity paradox exists saying that previous studies showing obesity as being protective may be confounded by a variety of pre-existing comorbidities, such as smoking.
Despite these recent findings, a group of scientists from UCLA offers evidence that the obesity paradox may be real.
The as-of-yet unpublished study, titled “The Obesity Paradox Characterizes Outcome from Acute Ischemic Stroke: Evidence from 1033 Patients”, will have its findings presented at the American Academy of Neurology’s 71st Annual Meeting. 
For the study, researchers examined 1,033 people (average age ~71 years old) who had experienced an acute ischemic stroke (AIS). For those of you not aware, a stroke occurs when the arteries supplying blood to the brain become blocked or narrowed, leading to severely reduced blood flow and oxygen delivery to the brain.
Average BMI for the 1000+ individuals 27.5, which puts them in the “overweight” classification (25-29.9). FYI, obese is having a BMI 30+.
Researchers segmented the 1,033 patients into one of five categories based on their BMI:
- Severely obese
Over the ensuing three months, researchers tracked the patients’ recovery and survival following the stroke.
At the end of the assessment period, researchers noted that the patients classified as “severely obese” has a 62% lower chance of dying from a stroke than individuals with a normal BMI. Obese individuals had a 46% reduced chance of dying in the ensuing 3 months following the stroke. 
Now, it should be noted that this study is observational, and as such, cannot give causality, meaning we cannot say that over fatness is the reason these people have a tendency to live longer following a stroke. Furthermore, only the study’s abstract is currently available as it has not been cleared for publication in any medical journal yet.
The authors offer up an explanation for why it appears that the obese and very obese seem to have a greater chance of survival:
“people who are overweight or obese may have a nutritional reserve that may help them survive during prolonged illness” 
Based on this, it appears that the researchers are implying that obese subjects are surviving due to the condition (obesity) that actually caused the problems (stroke) in the first place?
Let’s explore some possible explanations for why this is occurring.
3 Reasons Overweight and Obese Survive Illnesses Longer
#1 - Fat Maybe Protective
Fat serves as the body’s energy reserves in times when food intake is low.
Following injury, illness, or accident, nutrient demands increase substantially. An overweight or obese individual has vastly greater energy reserves to support the body’s demands as opposed to an individual of lower body weight.
If underweight people cannot intake sufficient amounts of essential nutrients, and they lack the bodily stores of energy to meet demand, they succumb to further illness, infection, and eventual death.
#2 - Underweight Individuals Have Less Muscle
Individuals who are underweight have less muscle mass than overweight and obese people simply due to the fact that they carry around less mass. As such, their body’s move less weight and thus have lower amounts of muscle.
Researchers have pretty clearly shown that lean mass is a key indicator of longevity, particularly in older adults, which is the population the most recent studied analyzed. 
Now, this can be addressed with consistent resistance training, proper diet, and adequate sleep, but by and large the average underweight person will have less muscle mass than the average overweight or obese person.
#3 - Differing Disease Progressions
While cardiovascular disease is a concern for both the extremely overweight and underweight, the progression of the disease (and its treatment) are substantially different.
For example, in a severely underweight person, high blood pressure, CVD, and diabetes, according to researchers, is more related to genetic factors than a consequence of the body weight, which makes the course of treatment more difficult to pin down.
In overweight and obese, hypertension and diabetes are treated using a mixture of lifestyle changes, including improvements to nutrition and an increase in physical activity. As individuals lose excess weight, blood pressure comes down and type 2 diabetes can be managed with a mixture of medication and diet.
The latest study shows that over the short term, excess body weight may improve subjects survival in the months immediately following an acute ischemic stroke. It says nothing in regards to long term risk of disease or all-cause mortality.
The studies that have assessed the effects of obesity over the long-term are pretty conclusive in that carrying excessive body weight and being overfat increase the risk of numerous diseases and ultimately yield a shorter lifespan.
Research continues to explore the myriad of ways obesity impacts the human body over the years, and this latest study is far from the proverbial “nail in the coffin” that obesity is healthy.
1) Gruberg, L., Weissman, N. J., Waksman, R., Fuchs, S., Deible, R., Pinnow, E. E., … Lindsay, J. J. (2002). The impact of obesity on the short-term and long-term outcomes after percutaneous coronary intervention: the obesity paradox? Journal of the American College of Cardiology, 39(4), 578–584.
2) Khan SS, Ning H, Wilkins JT, et al. Association of Body Mass Index With Lifetime Risk of Cardiovascular Disease and Compression of Morbidity. JAMA Cardiol. 2018;3(4):280–287. doi:10.1001/jamacardio.2018.0022
3) Stamatina Iliodromiti, Carlos A Celis-Morales, Donald M Lyall, Jana Anderson, Stuart R Gray, Daniel F Mackay, Scott M Nelson, Paul Welsh, Jill P Pell, Jason M R Gill, Naveed Sattar. The impact of confounding on the associations of different adiposity measures with the incidence of cardiovascular disease: a cohort study of 296 535 adults of white European descent. European Heart Journal, 2018; DOI: 10.1093/eurheartj/ehy057
4) European Society of Cardiology. "Study of nearly 300,000 people challenges the 'obesity paradox'." ScienceDaily. ScienceDaily, 15 March 2018. <www.sciencedaily.com/releases/2018/03/180315203916.htm>.
5) American Academy of Neurology, www.aan.com/PressRoom/Home/GetDigitalAsset/12895.
6) Srikanthan P, Karlamangla AS. Muscle mass index as a predictor of longevity in older adults. Am J Med. 2014;127(6):547-53.