Why Has Obesity Exploded in a Single Generation?

Updated July 2026

GLP-1 medications get discussed as if obesity were a simple problem waiting for the right drug. But before any conversation about the drugs makes sense, it's worth understanding the problem they're aimed at — because the story of how we got here explains both why these medications work and why they don't cure anything.

Start with a single sentence that reframes the whole issue: obesity happens when normal people do normal things in an abnormal environment. Sit with that for a moment. It moves the question away from personal failure and toward the world we're all living in.

How much has obesity actually changed?

Enormously, and fast. If you grew up in the 1960s or 1970s, you've watched the population around you grow visibly heavier. The CDC's obesity prevalence maps show it starkly: between 1990 and 2010, in just twenty years, the country went from mildly overweight to markedly overweight, and the maps have only worsened since.

Could genetics explain it?

No. Twenty years is far too short for a population-wide genetic shift. Our genes haven't changed meaningfully in that window — evolution doesn't move at that speed. So whatever happened, it wasn't written into our DNA.

Is it that we stopped trying?

Also no, and this is where the usual explanations fall apart. We haven't gotten lazier or more indifferent. Gym memberships and running participation have climbed for decades. And we clearly haven't stopped caring — at any given time, a large share of Americans are actively trying to lose weight, and we collectively spend tens of billions of dollars a year on weight-loss products, not counting medications. If effort were the answer, we'd be the leanest generation in history.

So what actually changed?

The food. Our food environment has been transformed in exactly the same window that obesity climbed — the grocery aisles, the restaurants, the drive-throughs all reshaped around cheap, hyperpalatable, calorie-dense products engineered to be easy to overeat. The environment changed, and it pulled our biology along with it.

Where do GLP-1 drugs fit into this?

They don't touch the environment at all. GLP-1 medications don't change what's stocked on shelves or served on menus. They change us — they alter our biology so we can tolerate an environment that's working against us. Put another way: if obesity happens when normal people do normal things in an abnormal environment, then GLP-1 drugs make normal people do abnormal things in that same abnormal environment. That's not a criticism of the drugs. It's just the clearest way to see what they are and aren't doing. To understand exactly how they pull that off, see how GLP-1 drugs work. And if the environment is the real driver, the obvious question is whether we can work with our biology instead of overriding it — which is where raising GLP-1 naturally with food comes in.

If you're new to this site and found this useful, I write one of these evidence-based articles every week. You can get them in your inbox by joining my email list at the bottom of this page. No spam, no requirement to buy anything, just practical knowledge.