The #1 Worst Thing Anyone Can Do for Their Health

Staying healthy has many factors—lifestyle choices, genetics, and environment all play a part. But if you asked the average doctor, "What's the worst thing a person could do to wreck their health"—or conversely, what's one change you can make to have the most far-reaching positive effects on health—chances are you'd get the same answer. Read on to find out more—and to ensure your health and the health of others, don't miss these Sure Signs You've Already Had COVID.

Pound for pound—pardon the pun—being overweight or obese is the worst thing you can do for your health. Carrying excess weight increases the risk of many serious diseases, compromises the immune system, and shortens lifespan. "From cancer to diabetes to heart disease, obesity increases the risk and severity of these medical conditions," John Magaña Morton, MD, a Yale Medicine obesity expert and division chief of bariatric and minimally invasive surgery, told ETNT Health. "When you add in that obesity decreases the effectiveness of medical treatment and raises the risk of complications during treatment, obesity is by far the most consequential health condition we have."

Obesity is determined by the body mass index (BMI). A BMI of 18 to 25 is considered normal, while a BMI over 25 is considered overweight. A BMI over 30 is considered obesity, which brings an increased risk for health problems.

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According to the Centers for Disease Control and Prevention, obesity is associated with an increased risk of the following serious health consequences:

• Death by any cause
• High blood pressure 
• High LDL ("bad") cholesterol, low HDL ("good") cholesterol, and high levels of triglycerides (a type of fat in the blood)
• Type 2 diabetes
• Heart disease
• Stroke
• Gallbladder disease
• Osteoarthritis 
• Sleep apnea 
• Several types of cancer 
• Mental illness
• Body pain and difficulty with physical functioning

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People tend to become obese because they regularly consume more calories than they expend. Some foods that are highly processed—including simple carbs, sweets, packaged snack foods and fast food—don't fill you up, and they encourage you to overeat. A diet that's heavy in processed foods like chips and cookies will increase a person's blood sugar, which can cause insulin to spike and crash, leading to frequent feelings of hunger. 

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Experts say there's no magic bullet (or diet) for weight loss. The key is to consume fewer calories. "The truth is, almost any diet will work [for weight loss] if it helps you take in fewer calories," says Harvard Medical School. 

So doctors advise eating high-quality calories, like those provided by the Mediterranean diet, which emphasizes fruits, vegetables, fish and olive oil, and is low in red meat, processed meats and processed foods. "The quality of the diet is much more important than the quantity of calories," says JoAnn Manson, MD, DrPH, professor of medicine at Harvard Medical School and chief of preventive medicine at Brigham & Women's Hospital. "A high-quality diet will almost automatically lead to better calorie control—you're going to be eating foods with higher satiety." And to get through this pandemic at your healthiest, don't miss these 35 Places You're Most Likely to Catch COVID.