This quote is from Peter Attia in his TED Talk from 2013. In that talk he tells a personal story from his days as an ER doctor that's both fascinating and heartbreaking and you should listen to it in his voice.
His point is fairly straight forward. We hear all the time that obesity is the enemy. That it's the cause of so many other problems; heart disease, high blood pressure, bad blood numbers (A1C, triglycerides, cholesterol) and the big-bad Type 2 diabetes. If you're fat you're in danger.
That may not be the point. We could be railing against the wrong enemy. As Dr Attia explains it's not being overweight that's the issue. It's insulin resistance that we should be fighting. That's the - many times - self induced situation brought on by years of high carb eating. Breakfast cereals and toast, giant sandwiches, pizza, cakes, cookies and desserts of all kinds add up to an overload of glucose until our cells are no longer able to utilize what, at that point, is an enormous amount of insulin. We've become resistant.
We all know people, whether we recognize them or not, who are normal weight, maybe even underweight, who are Type 2 diabetic and obese people who are otherwise pretty healthy. These aren't anomalies. It's the way the body works. You can be insulin resistant and not be overweight. You can be a few, or more, pounds overweight and not be fatally unhealthy.
Insulin resistance is the danger. It can sneak up on you. If you're looking in the mirror and are just assuming that's if you're not fat that you're healthy you could be making a terrible mistake. Go to your yearly physical and pay attention to your numbers, especially blood sugar and impaired glucose tolerance. If your doc uses words like "borderline pre-diabetic" pay attention and do something about it. (If he says "nothing to worry about" get a new doctor.) These are symptoms and harbingers of stuff you don't want to mess with.
PS Here's a fun way to learn more about insulin resistance and metabolic syndrome.