- [Sheena] The ideal sign of health used to be this, but fat fell out of fashion by the 19th century.

And ever since then, diets and weight loss have been a huge part of our lives.

- Everywhere you look, there's something about diets.

Diet culture basically surrounds us.

You have meal plans, and cleanses and supplements, all promising that lowering your body weight will improve your health and appearance.

- And do these diets even really work?

Does weight loss really have anything to do with making you healthy?

Dr. Jeffrey Hunger is a social psychologist that specializes in diet culture, weight stigma and health.

And I must say, the name is super fitting.

Okay, Dr.

Hunger, we can't wait to hear from you.

Tell us what is your take on some of these popular diets?

- If any of them really had the impact that they claimed?

We probably wouldn't see the new diets popping up left and right.

So we know that these diets don't make folks healthier, and oftentimes they do the exact opposite.

- Let's start by looking at the science behind some of the most popular diets.

- [Alok] Now, almost every diet out there boils down into one of three categories that get repackaged and then marketed to you.

You have high fat, low carb, low fat, high carb, and then calorie restriction where you can essentially eat whatever you want within a certain timeframe.

- [Sheena] Let's start with the diet that's been at the top of Google Health and diet searches for several years running.

It's called the ketogenic diet, or more popularly known as keto.

The keto diet was first introduced in the 1920s as a medical diet to help control seizures in people with epilepsy.

With only a moderate amount of protein and ultra low carbs, this diet is powered by fat and lots of it.

- And keeping those carbs ultra low is important because it mimics starvation and ultimately causes you to lose weight.

Let me explain.

Normally the body runs on carbs.

These complex strings of carbon, hydrogen and oxygen are broken down and used as a body's primary source of fuel.

When we shift to a diet that's high in fat, we take away that primary fuel source.

Without it, the body converts fat into chemicals called ketones.

In the absence of glucose, ketones act as an alternative source of fuel.

When your body runs in this state, it's called ketosis, hence, this diet's name.

- The diet is popular because in the short term, you lose weight fast, though it's mostly water weight, and not fat.

- And also this diet can be dangerous for people with certain underlying medical conditions such as kidney disease.

Now, going in the opposite direction is another category of diets.

That's high carb, low fat.

And one of the most popular is the Ornish diet.

This high carb, low fat, vegetarian diet makes an exception for fat free dairy products and egg whites.

But it forbids that you eat a lot of fats that many would consider healthy like coconut, margarine, nuts, seeds, olives and avocados.

Now, while the diet isn't necessarily bad, it's hard to draw conclusions about its overall effectiveness because it's part of a program that includes a lot of other lifestyle changes.

- One downside is that if they go overboard and their fat intake is too low, they can become deficient in essential fatty acids, which can cause several health problems like dry hair and skin, and that's a no.

Lastly there's intermittent fasting, which falls into a category of diets that reduces a person's calorie intake.

- Intermittent fasting, basically, is whether to eat or not eat.

That's the question.

The answer depends on your approach to fasting.

There's periodic fasting, time restricted fasting, alternate day fasting and others.

- Even though there are studies in humans that show that fasting can lead to a reduction in disease, they still haven't proved that there are long term health benefits.

Unlike keto, it can take a few days sometimes even weeks of fasting regularly for the body to start burning fat for fuel.

- There's nothing really magical about intermittent fasting.

It's a calorie restriction diet.

You're taking in less calories throughout the day because you're making less time to eat, shocking.

- But I can tell you being a nurse, working 13 hour shifts, I coincidentally end up doing intermittent fasting because obviously we're supposed to have breakfast, lunch and dinner in that amount of hours, And we definitely don't.

How about you Alok?

What worked, what didn't work?

What did you find out?

- What worked best for me, which is not really a diet, was actually keeping a journal and recording what I was eating, when, why I was eating that and how I felt afterwards.

Like my energy level, my sleep, my stress, all of it.

And I just became more mindful about my diet and that, to me, was more sustainable.

And I have, like better results because of it.

Bottom line is, most diets don't work when it comes to weight loss in the long term.

- Did you notice that these diets eliminate certain foods and even entire food groups?

That can be unhealthy and even impractical for some people.

Imagine never eating fruit again.

This is why a lot of dieters can lose the weight but they fail to keep it off.

- About 80% of people who went on a diet, regained the weight they lost after 12 months.

Would you try something if there was an 80% chance of failure after just one year?

- And counter-intuitively, when we cut back on calories, the body tries to conserve energy by slowing metabolism which makes it harder to lose weight in the future.

There's actual evidence of this.

- There is.

Six years after, the weight loss reality show, "The Biggest Loser," scientists did a follow up study on 14 contestants and they found that 13 had regained the weight they lost.

And also their resting metabolic rate, the amount of calories you use up during rest, actually slowed down.

So they had to eat less to maintain the same weight.

- Diets can also backfire by creating unhealthy habits that cause people to overeat.

In a fascinating series of psychological experiments starting in the 1970s, participants were given milkshakes, and then asked to taste and rate other foods.

After filling up on the milkshake, most testers ate less, but the dieters did the opposite.

They indulged and ate more.

Researchers coined this as the "what-the-hell-effect" because once dieters blew their diet, they figured, might as well keep on eating.

- What the hell is right.

If trying to lose weight is gonna cause you to develop unhealthy habits and skip meals then you gotta ask yourself, "Is the process of losing weight really a healthy one?"

Here's the thing, the relationship between weight and health isn't as clear as it seems.

- We're learning that different people can be healthy at different weights, and race can play as huge role.

As a black woman, I've seen data that says that I can be healthy at a higher BMI, while I've also seen data that says that Asian people can have increased health risks like diabetes at a lower BMI.

So things aren't always so clear-cut.

- We need to move beyond this laser focus on weight to actual indicators of health.

And there are plenty of them.

There are health behaviors, there are actual indicators of health that we can get when we go to the doctor.

Anything that moves beyond this very simplistic and very, very wrong assumption that weight is going to be the be all, end all when it comes to health.

- [Alok] 30% of individuals with normal weight were actually metabolically unhealthy.

And then 36% of individuals who would be classified as overweight or obese, were found to be metabolically healthy.

So the point is, weight alone is not synonymous with health.

According to the CDC, 74% of Americans are considered to be either overweight or obese.

Now science says that body weight is correlated to several human diseases, but there's a lot of other factors to consider.

I mean, obesity is a complex condition, and a lot of things can cause it such as genes, hormones, too little physical activity, diet, even viruses can play a role.

- Not to mention social and environmental factors like pollution, access to healthy foods and poverty.

We're not saying that higher weights don't correlate to more health risk, but it's more complex than you think.

- If we are just thinking about things at the individual level, and not thinking about how all of these health issues are a function of much broader social and structural conditions we're missing in.

- Now, come on in, we need to talk about something.

Let's debunk a popular myth.

Shaming people into losing weight, does not work.

Other people's weight, believe it or not, ain't your business, No fat shaming.

- None!

And also all this shame and anxiety and stigma, increases stress, which increases levels of cortisol, a stress hormone in your body.

And one of the jobs of cortisol, is to signal your body to store more fat.

Sheena, let me tell you straight up, that I have personally talked to teenage patients of mine, who are metabolically healthy.

They may be at a higher weight or BMI, but they're healthy.

But, they'll look at like, ads for certain gyms, and they'll scroll their Instagram and be like, "I don't look like that person, I'm not healthy."

And that leads to some bad behaviors, and like, that's a stigma that we gotta break.

- Right, some of it is genetics and we can't change that, but healthy, is individual people.

That's the main point that we're trying to really hone in on.

- Ding, ding, ding, ding, ding, ding, ding.

- So not surprisingly, if we are not out there shaming people for their weight, there are healthier outcomes.

They're more likely to go to the doctor, they're more likely to exercise, they're more likely to have a better diet.

Like, shaming folks makes absolutely no sense if we think it's a tool for health promotion.

- And one way, is to not focus on eating, but focus on healthy eating habits.

Instead of just absentminded snacking while you're at the desk, something I totally do.

We can be more mindful of what we eat and why.

Being more self aware of what triggers you to snack, can actually improve your relationship with food.

And that's a good thing.

- And can we stop moralizing it?

Food doesn't have to be good or bad, or sinful or guilt free.

It's just food.

Changing our language can help take the judgment out of eating and help people regain confidence in their own eating habits.

And a part of this is also sometimes enjoying the occasional treat.

It can help people regain balance and reduce that feeling of deprivation that causes so many of us to overeat.

- Eating should be enjoyable.

Like, and it should be a way for us to connect with our friends, connect with our family, connect with our culture.

- And let's stop giving food so much power.

There's so many factors involved in your health.

Take exercise.

Exercise alone won't help you lose that much weight, but it's excellent for your overall health.

In fact, most mortality risks that are associated with being heavier, are lessened in people who are physically active.

- You know, research shows that simply getting those steps in each day, simply walking and meeting those step goals, regardless of how vigorous they are, can actually reduce mortality risk.

So it's not about finding some marathon for you to run.

It's about finding something that works for you.

- And it's easy to forget that sleep can impact weight too.

When we don't get enough sleep, ghrelin, our hunger hormone goes up.

So prioritizing sleep can help us support a healthy body weight.

And coming from a very tired night shift nurse, I concur.

We forgot to say something really important, Alok.

It's about how you feel.

A diet should make you feel better, you should feel less bloated, you should have a better digestive day, you should be able to go to the bathroom more.

All of these things are important, and it's not just which the scale says.

- For sure.

Sleep better, better mental health, all of it.

Overall better relationship with your body.

That's what a diet should give you.

So remember, in order for a diet to actually be effective, you have to be able to stick with it in the long term.

And for many of us that means ditching the fat diets and the diet culture and focusing more on a sustainable overall strategy for your health.

- So ask yourself, "What diet fits comfortably in your lifestyle?"

And can you maintain it?

Let us know in the comments.

- There is so much to talk about.

We can't cover it all in one video, but we want to hear from you, your stories, your questions or comments.

So hit us up @PBSVitals.

We'll see you next time.

Now go snack on something, and don't feel guilty about it.

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