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Three and a half years ago,

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I made one of the best decisions of my life.

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As my New Year's resolution,

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I gave up dieting, stopped worrying about my weight,

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and learned to eat mindfully.

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Now I eat whenever I'm hungry,

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and I've lost 10 pounds.

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This was me at age 13,

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when I started my first diet.

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I look at that picture now, and I think,

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you did not need a diet,

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you needed a fashion consult.

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(Laughter)

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But I thought I needed to lose weight,

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and when I gained it back,

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of course I blamed myself.

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And for the next three decades,

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I was on and off various diets.

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No matter what I tried,

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the weight I'd lost always came back.

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I'm sure many of you know the feeling.

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As a neuroscientist,

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I wondered, why is this so hard?

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Obviously, how much you weigh depends on

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how much you eat and how much energy you burn.

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What most people don't realize

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is that hunger and energy use

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are controlled by the brain,

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mostly without your awareness.

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Your brain does a lot of its work behind the scenes,

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and that is a good thing,

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because your conscious mind --

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how do we put this politely? --

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it's easily distracted.

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It's good that you don't have to remember to breathe

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when you get caught up in a movie.

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You don't forget how to walk

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because you're thinking about
what to have for dinner.

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Your brain also has its own sense

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of what you should weigh,

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no matter what you consciously believe.

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This is called your set point,

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but that's a misleading term,

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because it's actually a range

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of about 10 or 15 pounds.

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You can use lifestyle choices to move your weight

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up and down within that range,

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but it's much, much harder to stay outside of it.

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The hypothalamus, the part of the brain

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that regulates body weight,

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there are more than a dozen chemical signals

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in the brain that tell your body to gain weight,

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more than another dozen that
tell your body to lose it,

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and the system works like a thermostat,

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responding to signals from the body

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by adjusting hunger, activity and metabolism,

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to keep your weight stable as conditions change.

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That's what a thermostat does, right?

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It keeps the temperature in your house the same

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as the weather changes outside.

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Now you can try to change the temperature

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in your house by opening a window in the winter,

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but that's not going to change
the setting on the thermostat,

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which will respond by kicking on the furnace

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to warm the place back up.

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Your brain works exactly the same way,

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responding to weight loss by using powerful tools

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to push your body back

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to what it considers normal.

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If you lose a lot of weight,

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your brain reacts as if you were starving,

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and whether you started out fat or thin,

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your brain's response is exactly the same.

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We would love to think that your brain could tell

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whether you need to lose weight or not,

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but it can't.

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If you do lose a lot of weight,

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you become hungry,

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and your muscles burn less energy.

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Dr. Rudy Leibel of Columbia University

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has found that people who have lost

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10 percent of their body weight

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burn 250 to 400 calories less

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because their metabolism is suppressed.

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That's a lot of food.

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This means that a successful dieter

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must eat this much less forever

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than someone of the same weight

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who has always been thin.

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From an evolutionary perspective,

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your body's resistance to weight loss makes sense.

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When food was scarce, our ancestors' survival

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depended on conserving energy,

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and regaining the weight when food was available

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would have protected them
against the next shortage.

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Over the course of human history,

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starvation has been a much bigger problem

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than overeating.

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This may explain a very sad fact:

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Set points can go up,

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but they rarely go down.

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Now, if your mother ever mentioned

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that life is not fair,

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this is the kind of thing she was talking about.

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(Laughter)

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Successful dieting doesn't lower your set point.

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Even after you've kept the weight off

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for as long as seven years,

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your brain keeps trying to make you gain it back.

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If that weight loss had been due to a long famine,

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that would be a sensible response.

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In our modern world of drive-thru burgers,

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it's not working out so well for many of us.

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That difference between our ancestral past

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and our abundant present

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is the reason that Dr. Yoni Freedhoff

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of the University of Ottawa

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would like to take some of his patients back to a time

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when food was less available,

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and it's also the reason

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that changing the food environment

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is really going to be the most effective solution

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to obesity.

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Sadly, a temporary weight gain

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can become permanent.

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If you stay at a high weight for too long,

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probably a matter of years for most of us,

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your brain may decide that that's the new normal.

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Psychologists classify eaters into two groups,

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those who rely on their hunger

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and those who try to control their eating

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through willpower, like most dieters.

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Let's call them intuitive eaters and controlled eaters.

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The interesting thing is that intuitive eaters

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are less likely to be overweight,

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and they spend less time thinking about food.

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Controlled eaters are more vulnerable

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to overeating in response to advertising,

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super-sizing, and the all-you-can-eat buffet.

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And a small indulgence,

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like eating one scoop of ice cream,

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is more likely to lead to a food binge

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in controlled eaters.

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Children are especially vulnerable

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to this cycle of dieting and then binging.

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Several long-term studies have shown

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that girls who diet in their early teenage years

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are three times more likely to become overweight

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five years later,

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even if they started at a normal weight,

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and all of these studies found

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that the same factors

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that predicted weight gain

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also predicted the development of eating disorders.

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The other factor, by the way,

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those of you who are parents,

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was being teased by family members

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about their weight.

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So don't do that.

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(Laughter)

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I left almost all my graphs at home,

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but I couldn't resist throwing in just this one,

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because I'm a geek, and that's how I roll.

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(Laughter)

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This is a study that looked at the risk of death

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over a 14-year period

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based on four healthy habits:

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eating enough fruits and vegetables,

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exercise three times a week,

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not smoking,

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and drinking in moderation.

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Let's start by looking at the normal weight

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people in the study.

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The height of the bars is the risk of death,

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and those zero, one, two, three, four numbers

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on the horizontal axis

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are the number of those healthy habits

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that a given person had.

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And as you'd expect, the healthier the lifestyle,

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the less likely people were to die during the study.

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Now let's look at what happens

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in overweight people.

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The ones that had no healthy habits

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had a higher risk of death.

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Adding just one healthy habit

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pulls overweight people back into the normal range.

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For obese people with no healthy habits,

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the risk is very high, seven times higher

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than the healthiest groups in the study.

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But a healthy lifestyle helps obese people too.

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In fact, if you look only at the group

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with all four healthy habits,

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you can see that weight makes very little difference.

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You can take control of your health

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by taking control of your lifestyle,

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even If you can't lose weight

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and keep it off.

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Diets don't have very much reliability.

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Five years after a diet,

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most people have regained the weight.

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Forty percent of them have gained even more.

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If you think about this,

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the typical outcome of dieting

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is that you're more likely to gain weight

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in the long run than to lose it.

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If I've convinced you that dieting

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might be a problem,

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the next question is, what do you do about it?

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And my answer, in a word, is mindfulness.

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I'm not saying you need to learn to meditate

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or take up yoga.

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I'm talking about mindful eating:

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learning to understand your body's signals

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so that you eat when you're hungry

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and stop when you're full,

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because a lot of weight gain boils down

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to eating when you're not hungry.

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How do you do it?

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Give yourself permission to eat

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as much as you want, and then work on figuring out

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what makes your body feel good.

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Sit down to regular meals without distractions.

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Think about how your body feels

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when you start to eat and when you stop,

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and let your hunger decide

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when you should be done.

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It took about a year for me to learn this,

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but it's really been worth it.

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I am so much more relaxed around food

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than I have ever been in my life.

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I often don't think about it.

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I forget we have chocolate in the house.

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It's like aliens have taken over my brain.

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It's just completely different.

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I should say that

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this approach to eating probably
won't make you lose weight

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unless you often eat when you're not hungry,

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but doctors don't know of any approach

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that makes significant weight loss in a lot of people,

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and that is why a lot of people are now focusing on

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preventing weight gain

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instead of promoting weight loss.

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Let's face it:

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If diets worked, we'd all be thin already.

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(Laughter)

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Why do we keep doing the same thing

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and expecting different results?

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Diets may seem harmless,

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but they actually do a lot of collateral damage.

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At worst, they ruin lives:

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Weight obsession leads to eating disorders,

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especially in young kids.

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In the U.S., we have 80 percent of 10-year-old girls

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say they've been on a diet.

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Our daughters have learned to measure their worth

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by the wrong scale.

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Even at its best,

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dieting is a waste of time and energy.

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It takes willpower which you could be using

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to help your kids with their homework

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or to finish that important work project,

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and because willpower is limited,

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any strategy that relies on its consistent application

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is pretty much guaranteed

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to eventually fail you

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when your attention moves on to something else.

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Let me leave you with one last thought.

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What if we told all those dieting girls

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that it's okay to eat when they're hungry?

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What if we taught them to work with their appetite

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instead of fearing it?

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I think most of them would be happier and healthier,

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and as adults,

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many of them would probably be thinner.

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I wish someone had told me that

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back when I was 13.

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Thanks.

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(Applause)