1 in 10 Deaths from Infectious Disease Are Caused by Obesity

• Mortality risk steadily climbed as BMI increased — People in the highest obesity class had a 2.75 times higher risk for severe nonfatal infections in the Finnish cohorts and 3.07 in the U.K. Biobank, meaning triple the risk compared to adults at a healthy weight.

For fatal infections, the danger was even higher. The risk reached 3.06 times in Finland and 3.54 times in the U.K., underscoring the magnitude of this problem.

• About 1 in 10 deaths from infectious disease are caused by obesity — After modeling the global impact, the researchers reported that 8.6% of all infection-related deaths in 2018 were attributable to obesity, rising to 15.0% during 2021 and settling at 10.8% (0.6 million out of 5.4 million) in 2023 as global conditions shifted due to the COVID-19 pandemic.

Another striking detail lies in how consistent the findings were across measurement methods. When the researchers evaluated obesity using waist circumference, waist-to-hip ratio, and body fat percentage, the risk remained almost identical — 1.7 times for severe infection across metrics. In short, excess fat, no matter how it’s measured, puts your health at risk.

• Infection severity was closely linked to obesity — The analyses included long follow-up periods, and captured infection events before, during, and after the COVID pandemic. Across all eras, the pattern held. Even when the COVID-19 pandemic entered the picture, the underlying risk landscape hardly budged.

Some groups experienced even steeper risk elevations than others. While the study reports strong effects across nearly everyone with obesity, individuals with class III obesity faced the largest surge in both hospitalizations and deaths.

• For context, obesity is currently broken down into three classes — Class I is a BMI of 30 to 34.9, and class II is a BMI of 35.0 to 39.9. Lastly, class III refers to a BMI of 40 or higher.⁵ Moving from overweight (BMI between 25 and 29.9) to class I obesity created a measurable rise in risk. However, advancing to class II and class III amplified the danger sharply.

• Excess fat tissue upsets metabolic health by keeping your body in a constant low-grade inflammatory state — As a result, immune function is also affected. According to the researchers, these include “(r)educed T-cell and NK-cell function, neutrophil dysfunction, dysregulated complement and adiponectin signalling, and diminished mucus clearance and lymphatic flow.”

• Higher body fat percentage equals higher infectious disease risk — The study reported the same pattern seen in The Lancet study — infections did not just simply occur more often in individuals with obesity; they progressed more aggressively.

According to the authors, “obesity has substantial effects on the immune system,” meaning the body’s internal security system struggles to respond effectively once pathogens enter when excess body fat gets in the way. The image below provides a summary of their theories:

• Excess adipose tissues (body fat) behave like an active endocrine organ — They release inflammatory hormones and chemical signals that disrupt communication between immune cells. In plain terms, the immune system loses coordination. When you live with this imbalance, you face a slower response to viruses and bacteria, which allows these microbes to multiply more easily.

• Obesity alters the architecture and function of the respiratory system — The authors explained that excess fat around the chest wall reduces lung expansion and lowers lung volumes, creating a mechanical disadvantage when the body tries to clear mucus or maintain airflow during an infection.

If you’ve ever felt out of breath walking up a short flight of stairs, this is the same limitation playing out at a microscopic level during a bout of respiratory illness. Bacteria and viruses take advantage of that reduced airflow, settling deeper into lung tissues.

• Inflammation persists for years in many obese individuals — Over time, this constant inflammatory pressure exhausts their immune cells. The review highlights that macrophages — the immune cells responsible for engulfing and clearing pathogens — switch into a less effective mode of activity under the influence of obesity-related inflammation. Instead of clearing invaders quickly, macrophages operate sluggishly, which prolongs infections and increases tissue damage.

• Respiratory infections often worsen the fastest, but skin issues aren’t far behind — Altered circulation reduces the body’s ability to deliver immune cells to the site of injury. However, changes in the skin also slow down wound-healing, allowing bacteria to enter your system faster.

• Excess skin due to obesity increases risk for topical infections — As body fat begins to increase, the skin compensates accordingly and causes more skin folds. The researchers noted that these are factors that increase the risk of fungal and bacterial skin infections.

• Obese individuals usually have existing nutrient deficiencies, which worsen the problem further — For example, vitamin D deficiency is far more common in adults with obesity. This nutrient plays an important role in immune function, especially in controlling inflammation in the respiratory tract.

• Adipose tissue in obesity recruits immune cells into fat stores, diverting them from circulation — This means that your body’s main protectors are pulled away from where infections unfold. As a result, when a pathogen enters through the lungs, skin, or gut, fewer active immune cells are available to meet the threat. Your body ends up fighting with a depleted army:⁷

“In obesity, visceral adipose tissue produces an excess of cytokines such as tumour necrosis factor α (TNFα) and interleukin (IL)-6 and 1β that could weaken the response of immune cells during an infectious stimulus,” the researchers explained.

“In addition, in a state of excess weight, a condition of hyperleptinemia is observed that can contribute to immune imbalance.”

1. Remove vegetable oils from your diet — Every time you eat ultraprocessed foods or food cooked in soybean, canola, corn, safflower, or sunflower oil, you push more LA into your tissues, slowing down your cellular energy production and nudging your body toward metabolic hibernation.

Once you reduce and eliminate these unhealthy oils from your diet, your cells stop fighting the inflammatory load and start burning fuel with far less strain. As this shift settles in, you feel more stable because your mitochondria burn energy cleanly.

I recommend keeping your LA intake under 3 grams a day. This amount aligns with the intake that our ancestors had before the rise of industrially made vegetable oils. To help you with accurate monitoring, sign up for the Mercola Health Coach app once it becomes available. It will contain a feature called a Seed Oil Sleuth, which will compile your daily LA intake to a tenth of a gram.

2. Choose stable fats to keep energy steady — Continuing the point above, when you trade out seed oils for healthier saturated fats like grass fed butter, coconut oil, ghee, and beef tallow, you give your metabolism a major advantage. These fats burn cleanly, support oxygen use, and help your cells stay switched on instead of drifting into storage mode. It’s the difference between running your engine on premium fuel versus watered-down gasoline.

3. Choose healthy carbs to maintain metabolic flexibility — Don’t be tempted to cut out carbs in an effort to lose weight because this forces your body into a low-oxygen, low-energy environment. When chosen carefully, carbs, especially healthy ones, protect your metabolism. That means choosing whole fruits, white rice, and root vegetables — foods that help promote proper cellular energy. Don’t choose refined and ultraprocessed carb sources.

4. Dial down stress — Feeling tense, overstimulated, or wired, especially at night, usually means that your cortisol and estrogen are running too high, pushing your system toward fat storage and suppress healthy energy production.

To lower your stress levels, remember to get daily sunlight and restful sleep, and minimize back on alcohol (or remove it entirely). As those stress signals drop, your metabolism burns energy better instead of hoarding it.

5. Teach your body to switch metabolic fuels through exercise — Staying inactive teaches your mitochondria to conserve rather than produce. Doing gentle strength training, daily walking, and light resistance exercise can wake them back up.

Movement tells your cells how to use both fat and carbs for energy, instead of locking into one inefficient mode. You don’t need extreme exercise — you only need consistent motion that challenges your muscles and keeps energy flowing.