For decades, if you were of low and mercenary character, there was no better business than the weight-loss industry. Many people with extra poundage will pay almost any price to slim down to a healthy and socially acceptable weight. And since none of the remedies worked for very long, the weight always returned, along with the customers.

Reading this, you’re probably thinking of social media figures and late-night infomercials promoting fad diets, snake oil supplements, quack gadgets and spartan exercise regimes. But the reason those charlatans were successful is that the decent people trying to help, backed by medical evidence, weren’t offering much better solutions.

WeightWatchers was one of the most credible players in a generally discreditable space. Its regime was sensible, healthy and designed to fit into everyday life. It also often failed. A 2007 study of almost 700 “lifetime members” of WeightWatchers, who had reached their goal weight and maintained it for at least six weeks, found that within five years the participants had regained most of the lost pounds.

Now WeightWatchers has filed for bankruptcy, because the sensible and medically approved advice failed to fix the actual reason people were overeating. Not because they didn’t realize what kind of food made you fat, or that they lacked willpower, or they needed to deal with deep-seated emotional issues. They were eating, quite simply, because they were hungry. And it took a drug, not a diet, to control it.

Hunger is a biological signal akin to pain. I don’t know about you, but I am a monster when I am really hungry: apt to drop important, time-sensitive projects so I can grab a bite; prone to barking at family members who stand between me and my dinner.

A lot of people aren’t so lucky, and they were the WeightWatchers customer base. Some peoples’ bodies simply want to be heavier than others - people like me tend to see their weight fluctuate somewhere between “underweight” and “normal” on the actuarial tables, even if we make no effort to control what we eat, while others are fighting a biological urge to store large amounts of fat. That grim reality has often been overlooked in the discourse around America’s obesity epidemic, because many basically thin people, who restrict their eating just enough to keep their weight near the bottom end of their natural range, tend to assume that really heavy people could do the same if they just exerted some effort.

As Gina Kolata pointed out in her 2007 book, “Rethinking Thin,” the seriously overweight were trying to do something very different: keep their weight permanently below the natural range where their body was comfortable. Their body reacted the way a thin person’s would if they were starving in a prisoner-of-war camp. Their metabolism slowed, and their hunger increased.

In recent years, there has been more recognition of that fact by public health experts. In a society rich enough to provide more than enough calories to everyone, there often wasn’t much we could do about weight gain, except for risky bariatric surgeries.

Instead, they offered solutions that didn’t work on a larger scale, such as fiddling with school lunches or complaining about capitalism. That is, right up until the capitalists delivered a drug that did what the public health experts couldn’t: fix the hunger.

I’ve found it sad and heartening to hear stories of friends who’ve tried them. One used to start planning dinner as he was finishing breakfast. Another said he’d never understood how people could leave food on their plate. Then they injected a drug, and like magic, their obsession with food melted away, along with the pounds.

This is a minor miracle, and we ought to treat it as such. But we can’t get over our feeling that there ought to be some other solution. Something in us wants WeightWatchers to work, as ardently as its frustrated customers did all those years. Despite all the evidence, we can’t quite let the old nostrums go.

Our secretary of health and human services wants to focus on American diets, in hopes that the same thing that didn’t work the last 100 million times might now suddenly succeed. “They’re counting on selling it to Americans because we’re so stupid and so addicted to drugs,” Robert F. Kennedy Jr. told Fox News last year, as though the makers of weight-loss drugs were somehow putting one over on us by solving an enormous health issue. I’ve heard these same arguments echoed by many others in real life, along with laments that the drugs stop working if you stop taking them (just like my blood pressure medicine).

But as markets have realized, the WeightWatchers model has decisively failed. Perhaps it was the best we could do at the time, but that time has thankfully passed. Obesity isn’t a social problem or personal flaw; it’s a biological problem, like my hypertension. Like my hypertension, it has a medical solution that works much better than telling me to reduce stress and eat less salt. And I, for one, am grateful we found it.

Megan McArdle is a Washington Post columnist