0:00:00.478,0:00:02.213
Three and a half years ago,

0:00:02.213,0:00:05.463
I made one of the best decisions of my life.

0:00:05.463,0:00:07.526
As my New Year's resolution,

0:00:07.526,0:00:11.765
I gave up dieting, stopped worrying about my weight,

0:00:11.765,0:00:14.790
and learned to eat mindfully.

0:00:14.790,0:00:18.673
Now I eat whenever I'm hungry,

0:00:18.673,0:00:21.736
and I've lost 10 pounds.

0:00:21.736,0:00:24.273
This was me at age 13,

0:00:24.273,0:00:26.813
when I started my first diet.

0:00:26.813,0:00:29.825
I look at that picture now, and I think,

0:00:29.825,0:00:31.659
you did not need a diet,

0:00:31.659,0:00:34.330
you needed a fashion consult.

0:00:34.330,0:00:36.737
(Laughter)

0:00:36.737,0:00:39.806
But I thought I needed to lose weight,

0:00:39.806,0:00:41.268
and when I gained it back,

0:00:41.268,0:00:45.196
of course I blamed myself.

0:00:45.196,0:00:47.703
And for the next three decades,

0:00:47.703,0:00:50.458
I was on and off various diets.

0:00:50.458,0:00:52.530
No matter what I tried,

0:00:52.530,0:00:55.361
the weight I'd lost always came back.

0:00:55.361,0:00:58.962
I'm sure many of you know the feeling.

0:00:58.962,0:01:00.523
As a neuroscientist,

0:01:00.523,0:01:03.337
I wondered, why is this so hard?

0:01:03.337,0:01:05.897
Obviously, how much you weigh depends on

0:01:05.897,0:01:08.487
how much you eat and how much energy you burn.

0:01:08.487,0:01:10.703
What most people don't realize

0:01:10.703,0:01:12.516
is that hunger and energy use

0:01:12.516,0:01:14.620
are controlled by the brain,

0:01:14.620,0:01:18.135
mostly without your awareness.

0:01:18.135,0:01:21.695
Your brain does a lot of its work behind the scenes,

0:01:21.695,0:01:23.911
and that is a good thing,

0:01:23.911,0:01:26.097
because your conscious mind --

0:01:26.097,0:01:27.964
how do we put this politely? --

0:01:27.964,0:01:31.239
it's easily distracted.

0:01:31.239,0:01:33.944
It's good that you don't have to remember to breathe

0:01:33.944,0:01:36.584
when you get caught up in a movie.

0:01:36.584,0:01:38.601
You don't forget how to walk

0:01:38.601,0:01:41.516
because you're thinking about[br]what to have for dinner.

0:01:41.516,0:01:43.500
Your brain also has its own sense

0:01:43.500,0:01:45.265
of what you should weigh,

0:01:45.265,0:01:48.327
no matter what you consciously believe.

0:01:48.327,0:01:50.367
This is called your set point,

0:01:50.367,0:01:52.033
but that's a misleading term,

0:01:52.033,0:01:53.743
because it's actually a range

0:01:53.743,0:01:56.307
of about 10 or 15 pounds.

0:01:56.307,0:01:59.530
You can use lifestyle choices to move your weight

0:01:59.530,0:02:01.598
up and down within that range,

0:02:01.598,0:02:06.003
but it's much, much harder to stay outside of it.

0:02:06.003,0:02:08.030
The hypothalamus, the part of the brain

0:02:08.030,0:02:09.943
that regulates body weight,

0:02:09.943,0:02:12.366
there are more than a dozen chemical signals

0:02:12.366,0:02:14.982
in the brain that tell your body to gain weight,

0:02:14.982,0:02:18.666
more than another dozen that[br]tell your body to lose it,

0:02:18.666,0:02:21.976
and the system works like a thermostat,

0:02:21.976,0:02:24.323
responding to signals from the body

0:02:24.323,0:02:27.931
by adjusting hunger, activity and metabolism,

0:02:27.931,0:02:31.657
to keep your weight stable as conditions change.

0:02:31.657,0:02:33.759
That's what a thermostat does, right?

0:02:33.759,0:02:37.191
It keeps the temperature in your house the same

0:02:37.191,0:02:39.951
as the weather changes outside.

0:02:39.951,0:02:42.773
Now you can try to change the temperature

0:02:42.773,0:02:46.269
in your house by opening a window in the winter,

0:02:46.269,0:02:50.035
but that's not going to change[br]the setting on the thermostat,

0:02:50.035,0:02:52.234
which will respond by kicking on the furnace

0:02:52.234,0:02:54.671
to warm the place back up.

0:02:54.671,0:02:57.993
Your brain works exactly the same way,

0:02:57.993,0:03:01.136
responding to weight loss by using powerful tools

0:03:01.136,0:03:02.290
to push your body back

0:03:02.290,0:03:06.320
to what it considers normal.

0:03:06.320,0:03:08.295
If you lose a lot of weight,

0:03:08.295,0:03:12.620
your brain reacts as if you were starving,

0:03:12.620,0:03:15.252
and whether you started out fat or thin,

0:03:15.252,0:03:18.217
your brain's response is exactly the same.

0:03:18.217,0:03:20.490
We would love to think that your brain could tell

0:03:20.490,0:03:21.956
whether you need to lose weight or not,

0:03:21.956,0:03:24.091
but it can't.

0:03:24.091,0:03:26.984
If you do lose a lot of weight,

0:03:26.984,0:03:29.283
you become hungry,

0:03:29.283,0:03:32.169
and your muscles burn less energy.

0:03:32.169,0:03:34.818
Dr. Rudy Leibel of Columbia University

0:03:34.818,0:03:36.527
has found that people who have lost

0:03:36.527,0:03:38.726
10 percent of their body weight

0:03:38.726,0:03:41.549
burn 250 to 400 calories less

0:03:41.549,0:03:44.057
because their metabolism is suppressed.

0:03:44.057,0:03:46.487
That's a lot of food.

0:03:46.487,0:03:48.711
This means that a successful dieter

0:03:48.711,0:03:51.879
must eat this much less forever

0:03:51.879,0:03:53.171
than someone of the same weight

0:03:53.171,0:03:55.474
who has always been thin.

0:03:55.474,0:03:57.264
From an evolutionary perspective,

0:03:57.264,0:03:59.808
your body's resistance to weight loss makes sense.

0:03:59.808,0:04:02.944
When food was scarce, our ancestors' survival

0:04:02.944,0:04:05.438
depended on conserving energy,

0:04:05.438,0:04:07.691
and regaining the weight when food was available

0:04:07.691,0:04:10.798
would have protected them[br]against the next shortage.

0:04:10.798,0:04:13.325
Over the course of human history,

0:04:13.325,0:04:16.327
starvation has been a much bigger problem

0:04:16.327,0:04:18.011
than overeating.

0:04:18.011,0:04:22.242
This may explain a very sad fact:

0:04:22.242,0:04:25.071
Set points can go up,

0:04:25.071,0:04:27.943
but they rarely go down.

0:04:27.943,0:04:30.132
Now, if your mother ever mentioned

0:04:30.132,0:04:32.428
that life is not fair,

0:04:32.428,0:04:35.221
this is the kind of thing she was talking about.

0:04:35.221,0:04:38.259
(Laughter)

0:04:38.259,0:04:41.444
Successful dieting doesn't lower your set point.

0:04:41.444,0:04:42.988
Even after you've kept the weight off

0:04:42.988,0:04:44.817
for as long as seven years,

0:04:44.817,0:04:48.790
your brain keeps trying to make you gain it back.

0:04:48.790,0:04:52.080
If that weight loss had been due to a long famine,

0:04:52.080,0:04:54.409
that would be a sensible response.

0:04:54.409,0:04:57.090
In our modern world of drive-thru burgers,

0:04:57.090,0:05:00.547
it's not working out so well for many of us.

0:05:00.547,0:05:04.290
That difference between our ancestral past

0:05:04.290,0:05:06.693
and our abundant present

0:05:06.693,0:05:08.982
is the reason that Dr. Yoni Freedhoff

0:05:08.982,0:05:11.042
of the University of Ottawa

0:05:11.042,0:05:13.743
would like to take some of his patients back to a time

0:05:13.743,0:05:15.842
when food was less available,

0:05:15.842,0:05:17.543
and it's also the reason

0:05:17.543,0:05:19.927
that changing the food environment

0:05:19.927,0:05:24.043
is really going to be the most effective solution

0:05:24.043,0:05:26.153
to obesity.

0:05:26.153,0:05:29.430
Sadly, a temporary weight gain

0:05:29.430,0:05:31.475
can become permanent.

0:05:31.475,0:05:34.109
If you stay at a high weight for too long,

0:05:34.109,0:05:36.583
probably a matter of years for most of us,

0:05:36.583,0:05:41.021
your brain may decide that that's the new normal.

0:05:41.021,0:05:45.081
Psychologists classify eaters into two groups,

0:05:45.081,0:05:46.699
those who rely on their hunger

0:05:46.699,0:05:49.268
and those who try to control their eating

0:05:49.268,0:05:55.331
through willpower, like most dieters.

0:05:55.331,0:06:01.842
Let's call them intuitive eaters and controlled eaters.

0:06:01.842,0:06:04.025
The interesting thing is that intuitive eaters

0:06:04.025,0:06:06.656
are less likely to be overweight,

0:06:06.656,0:06:10.358
and they spend less time thinking about food.

0:06:10.358,0:06:14.002
Controlled eaters are more vulnerable

0:06:14.002,0:06:16.865
to overeating in response to advertising,

0:06:16.865,0:06:20.728
super-sizing, and the all-you-can-eat buffet.

0:06:20.728,0:06:22.473
And a small indulgence,

0:06:22.473,0:06:25.679
like eating one scoop of ice cream,

0:06:25.679,0:06:31.289
is more likely to lead to a food binge

0:06:31.289,0:06:33.186
in controlled eaters.

0:06:33.186,0:06:35.113
Children are especially vulnerable

0:06:35.113,0:06:38.242
to this cycle of dieting and then binging.

0:06:38.242,0:06:41.071
Several long-term studies have shown

0:06:41.071,0:06:45.223
that girls who diet in their early teenage years

0:06:45.223,0:06:48.548
are three times more likely to become overweight

0:06:48.548,0:06:50.085
five years later,

0:06:50.085,0:06:52.904
even if they started at a normal weight,

0:06:52.904,0:06:55.553
and all of these studies found

0:06:55.553,0:06:57.860
that the same factors

0:06:57.860,0:07:01.254
that predicted weight gain

0:07:01.254,0:07:04.254
also predicted the development of eating disorders.

0:07:04.254,0:07:05.822
The other factor, by the way,

0:07:05.822,0:07:07.251
those of you who are parents,

0:07:07.251,0:07:10.480
was being teased by family members

0:07:10.480,0:07:11.991
about their weight.

0:07:11.991,0:07:13.827
So don't do that.

0:07:13.827,0:07:15.565
(Laughter)

0:07:15.565,0:07:18.201
I left almost all my graphs at home,

0:07:18.201,0:07:20.494
but I couldn't resist throwing in just this one,

0:07:20.494,0:07:22.907
because I'm a geek, and that's how I roll.

0:07:22.907,0:07:25.386
(Laughter)

0:07:25.386,0:07:27.734
This is a study that looked at the risk of death

0:07:27.734,0:07:29.600
over a 14-year period

0:07:29.600,0:07:32.102
based on four healthy habits:

0:07:32.102,0:07:34.222
eating enough fruits and vegetables,

0:07:34.222,0:07:36.448
exercise three times a week,

0:07:36.448,0:07:37.824
not smoking,

0:07:37.824,0:07:39.794
and drinking in moderation.

0:07:39.794,0:07:41.723
Let's start by looking at the normal weight

0:07:41.723,0:07:43.311
people in the study.

0:07:43.311,0:07:45.198
The height of the bars is the risk of death,

0:07:45.198,0:07:47.579
and those zero, one, two, three, four numbers

0:07:47.579,0:07:48.825
on the horizontal axis

0:07:48.825,0:07:50.858
are the number of those healthy habits

0:07:50.858,0:07:52.418
that a given person had.

0:07:52.418,0:07:55.407
And as you'd expect, the healthier the lifestyle,

0:07:55.407,0:07:58.319
the less likely people were to die during the study.

0:07:58.319,0:07:59.641
Now let's look at what happens

0:07:59.641,0:08:01.487
in overweight people.

0:08:01.487,0:08:03.559
The ones that had no healthy habits

0:08:03.559,0:08:05.330
had a higher risk of death.

0:08:05.330,0:08:07.094
Adding just one healthy habit

0:08:07.094,0:08:10.556
pulls overweight people back into the normal range.

0:08:10.556,0:08:13.298
For obese people with no healthy habits,

0:08:13.298,0:08:16.008
the risk is very high, seven times higher

0:08:16.008,0:08:18.144
than the healthiest groups in the study.

0:08:18.144,0:08:22.084
But a healthy lifestyle helps obese people too.

0:08:22.084,0:08:24.602
In fact, if you look only at the group

0:08:24.602,0:08:26.876
with all four healthy habits,

0:08:26.876,0:08:29.488
you can see that weight makes very little difference.

0:08:29.488,0:08:31.544
You can take control of your health

0:08:31.544,0:08:33.418
by taking control of your lifestyle,

0:08:33.418,0:08:34.899
even If you can't lose weight

0:08:34.899,0:08:36.635
and keep it off.

0:08:36.635,0:08:40.745
Diets don't have very much reliability.

0:08:40.745,0:08:42.522
Five years after a diet,

0:08:42.522,0:08:45.310
most people have regained the weight.

0:08:45.310,0:08:47.792
Forty percent of them have gained even more.

0:08:47.792,0:08:49.217
If you think about this,

0:08:49.217,0:08:51.564
the typical outcome of dieting

0:08:51.564,0:08:53.452
is that you're more likely to gain weight

0:08:53.452,0:08:56.221
in the long run than to lose it.

0:08:56.221,0:08:59.075
If I've convinced you that dieting

0:08:59.075,0:09:01.104
might be a problem,

0:09:01.104,0:09:03.742
the next question is, what do you do about it?

0:09:03.742,0:09:08.198
And my answer, in a word, is mindfulness.

0:09:08.198,0:09:10.733
I'm not saying you need to learn to meditate

0:09:10.733,0:09:12.725
or take up yoga.

0:09:12.725,0:09:15.277
I'm talking about mindful eating:

0:09:15.277,0:09:18.785
learning to understand your body's signals

0:09:18.785,0:09:21.174
so that you eat when you're hungry

0:09:21.174,0:09:23.516
and stop when you're full,

0:09:23.516,0:09:25.694
because a lot of weight gain boils down

0:09:25.694,0:09:28.760
to eating when you're not hungry.

0:09:28.760,0:09:30.244
How do you do it?

0:09:30.244,0:09:32.078
Give yourself permission to eat

0:09:32.078,0:09:34.283
as much as you want, and then work on figuring out

0:09:34.283,0:09:36.035
what makes your body feel good.

0:09:36.035,0:09:39.764
Sit down to regular meals without distractions.

0:09:39.764,0:09:41.563
Think about how your body feels

0:09:41.563,0:09:43.617
when you start to eat and when you stop,

0:09:43.617,0:09:46.104
and let your hunger decide

0:09:46.104,0:09:47.572
when you should be done.

0:09:47.572,0:09:49.993
It took about a year for me to learn this,

0:09:49.993,0:09:51.764
but it's really been worth it.

0:09:51.764,0:09:54.849
I am so much more relaxed around food

0:09:54.849,0:09:57.712
than I have ever been in my life.

0:09:57.712,0:10:00.277
I often don't think about it.

0:10:00.277,0:10:03.010
I forget we have chocolate in the house.

0:10:03.010,0:10:05.954
It's like aliens have taken over my brain.

0:10:05.954,0:10:08.712
It's just completely different.

0:10:08.712,0:10:11.378
I should say that

0:10:11.378,0:10:14.171
this approach to eating probably[br]won't make you lose weight

0:10:14.171,0:10:17.088
unless you often eat when you're not hungry,

0:10:17.088,0:10:20.986
but doctors don't know of any approach

0:10:20.986,0:10:25.461
that makes significant weight loss in a lot of people,

0:10:25.461,0:10:28.831
and that is why a lot of people are now focusing on

0:10:28.831,0:10:30.990
preventing weight gain

0:10:30.990,0:10:34.213
instead of promoting weight loss.

0:10:34.213,0:10:35.749
Let's face it:

0:10:35.749,0:10:39.960
If diets worked, we'd all be thin already.

0:10:39.960,0:10:41.860
(Laughter)

0:10:41.860,0:10:43.497
Why do we keep doing the same thing

0:10:43.497,0:10:46.380
and expecting different results?

0:10:46.380,0:10:48.063
Diets may seem harmless,

0:10:48.063,0:10:51.781
but they actually do a lot of collateral damage.

0:10:51.781,0:10:54.216
At worst, they ruin lives:

0:10:54.216,0:10:56.532
Weight obsession leads to eating disorders,

0:10:56.532,0:10:59.475
especially in young kids.

0:10:59.475,0:11:04.353
In the U.S., we have 80 percent of 10-year-old girls

0:11:04.353,0:11:06.130
say they've been on a diet.

0:11:06.130,0:11:08.391
Our daughters have learned to measure their worth

0:11:08.391,0:11:11.494
by the wrong scale.

0:11:11.494,0:11:13.519
Even at its best,

0:11:13.519,0:11:16.247
dieting is a waste of time and energy.

0:11:16.247,0:11:20.469
It takes willpower which you could be using

0:11:20.469,0:11:23.091
to help your kids with their homework

0:11:23.091,0:11:26.707
or to finish that important work project,

0:11:26.707,0:11:30.194
and because willpower is limited,

0:11:30.194,0:11:34.817
any strategy that relies on its consistent application

0:11:34.817,0:11:37.600
is pretty much guaranteed

0:11:37.600,0:11:39.693
to eventually fail you

0:11:39.693,0:11:43.542
when your attention moves on to something else.

0:11:43.542,0:11:47.474
Let me leave you with one last thought.

0:11:47.474,0:11:50.377
What if we told all those dieting girls

0:11:50.377,0:11:53.378
that it's okay to eat when they're hungry?

0:11:53.378,0:11:55.628
What if we taught them to work with their appetite

0:11:55.628,0:11:57.753
instead of fearing it?

0:11:57.753,0:12:01.180
I think most of them would be happier and healthier,

0:12:01.180,0:12:03.195
and as adults,

0:12:03.195,0:12:06.968
many of them would probably be thinner.

0:12:06.968,0:12:09.081
I wish someone had told me that

0:12:09.081,0:12:12.502
back when I was 13.

0:12:12.502,0:12:14.508
Thanks.

0:12:14.508,0:12:22.867
(Applause)