Eating smaller and smaller portions won't help you lose weight in a healthy way. Shutterstock Obesity is not a character flaw; it's a medical issue. That's why we need to stop blaming weight gain on willpower.

If you've tried dieting, you know that cutting calories is only a temporary fix.

Lindsey Averill knows this fact firsthand.

When she was younger, Averill went through a period when she would only eat 400 calories a day to try to slim down — a fraction of the 2,000 calories or so most people need to function properly.

She has long since stopped starving herself, and today, at 37, Averill eats a healthy, balanced diet and swims 5 miles a week.

"I do eat less than a thin person, and I do exercise, and I’m still fat," Averill told Tech Insider. "I don't know if there’s a magic way of eating that would stop that."

There's a widespread misconception that eating less and exercising are a panacea for losing weight and keeping it off. But that isn't always true.

"Body weight is controlled more by our biology than by our willpower," Dr. David Ludwig, a Harvard Medical School nutrition and obesity expert, told Tech Insider. "When we cut back on calories — as virtually all conventional diets require us to do in one way or another — yes, you'll start losing weight, but the body fights back."

How exactly does it fight back? Ludwig explained: "The first thing that happens is you get hungrier. Hunger isn't just a passing feeling. It's a primal biological signal that your body needs calories." And that signal is difficult, sometimes painful to ignore — even for someone with an iron will.

Over the years, Averill has learned to embrace her body, and she's helping others to do the same. She teamed up with Viridiana Lieberman to make the documentary "Fattitude" about ending fat shaming and spreading body positivity.

"For us, [it] has to do with civil rights and social respect ... We want to make the argument that I should be treated as a human being no matter what," she said. "The thing about prejudice about fat people is you can talk to someone who totally gets sexism and totally gets racism, and they will not get what fat people go through. It's still unchecked."

Studies have found that weight discrimination has increased by 66% over the past decade, and is even widespread among doctors. Over two-thirds of fat people say their doctors have discriminated against them.

Doctors are the ones who should be able to help their patients lose weight if they want to. But that needs to start from a place of trust and mutual respect.

Averill said she recently had a stranger tell her she should eat 1,000 fewer calories. But they didn't know how many calories she eats, she said, so how could they possibly make the assumption that she should cut back? What if she was only eating 1,000 calories a day?

According to Ludwig, this kind of widespread social discrimination only makes the problem worse.

"Simply exhorting people to eat less and move more is not only futile, but it implicitly blames people for the failure of the paradigm," Ludwig said. "It sounds so simple that if you can't do it ('eat less and move more'), it must be your fault. You're either undisciplined, or worse — you have a character problem. People get stigmatized. First of all, they blame themselves, they feel ashamed, and society jumps in to blame them as well, explaining why people with this particular medical problem experience much more stigmatization, abuse, and discrimination than virtually any other medical problem."

And this stigma is exactly what Averill hopes to eradicate.

"I think we need to allow people to forge their own paths," she said. "At the end of the day, what you can do for yourself is to make the right choices for your body."