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Susan B. Roberts, PhDProfessor of Nutrition & Professor of Psychiatry

Director of the Energy Metabolism Laboratory, USDA Nutrition CenterScientific Staff Member in Pediatrics

Tufts University and Tufts Medical School

How, as individuals, should we approach nutrition and healthy

weight control?

How To Weigh Yourself And Get The Most Accurate Results

“I can’t believe I was doing it wrong all these years.”

Some Statistics

Rates of obesity started rising in the mid-1980s- Adults: 2/3 now overweight or obese- Children: 1/5 now ow/obese and rising

51% adults diet in any given year

Using currently available diet methods, people who intentionally lose weight typically regain all lost weight

Energy Balance and Weight Control in Adults

Consumed Expended

kcal

/day

• To prevent obesity, energy intake = total energy expenditure

• Weight gain happens when intake > expenditure.

• Removing all the causes of weight gain creates neutral not negative energy balance.

• It’s easy to overeat, hard to undereat! The 2/3 population who are overweight/obese need effective methods for sustainable negative energy balance

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2000

1500

1000

500

3000

Love of good food!

Big portions

Stress-eating

Eating out a lot

Holidays & vacations

Lack of exercise

Pregancy-gain

Decreasing metabolism

Bo

dy

Fa

t (%

)

Net Energy Cost of Exercise Training Per Week (1000 kcal)1 2 3 4 5 60

45

40

35

30

25

20

15

10

Bo

dy

Fa

t (%

)

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Regression of Change in Women

1 2 3 4 5 60

Summary of Changes in Body Fat in 50 Long-Term Exercise Intervention StudiesElder & Roberts. Nutr Rev 2007;65:1

• 1 hr/day absolute max achieved (less in women)

• Small effect exercise on fatness

• 1 hr/d of jogging -3.5% body fat over 6 mo (≈6 lb weight)

Regression of Change in Men

What Happened?

1000

1500

2000

2500

3000

19751980

19851990

20002005

1995Per

Cap

ita F

ood

Sup

ply

Cor

rect

ed fo

r W

aste

(kca

l/day

)

• Increase of 564 kcal/d in food supply.

• 2 foods account for most of the increase: - high fructose corn syrup - oil

• 4 more contribute a bit: - flour - cheese - shortening - edible beef tallow

• What didn’t increase: beef, seafood, candy, chocolate, chips, cream (and ice cream and frozen desserts decreased 13%)

•

A problem of energy intake or energy expenditure?

Weight loss and prevention of weight regain require reducing energy intake relative to energy expenditure. Given the 500+ calorie increase in energy intake since 1975, a decrease in energy intake is easily justified as practical solution

Amounts of exercise required to reduce BMI values to a healthy range unlikely to be achievable and therefore hard to justify as practical solution

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Is reducing energy intake a society problem or and individual problem?

Restaurants as one example of our food environment, and their impact broadly

considered

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Multi-Site Study of Randomly-Selected Restaurant FoodsUrban et al. JAMA 2011

• Study of 269 randomly selected restaurant foods from MA, AR, IN

• Average stated calories were accurate BUT low calorie foods in sit-down restaurants contained 7% more calories than stated.

• Sides on average contained more calories than the entrée they accompanied.

• Estimated impact on body weight if self-monitoring energy intake: ≈+10 lb/year

Excess Energy Intake Relative to Requirements in Most Restaurant Meals

(Urban et al, in preparation)

500 kcal

• Study of 170 restaurant meals from 9 most popular ethnic categories in 36 randomly selected restaurants in Greater Boston area

• Average stated calorie contents were 1276 kcal.

667 kcal

• Represents 2.0-2.5 times healthy meal size for maintaining energy balance, and ≈100% daily energy intake for individual trying to lose weight.

Why do humans eat the way they do and like the things they like?

• Moviegoers were given free popcorn - fresh or stale - medium or large.

• Amount consumed was significantly greater for larger

portions even when the popcorn was stale.

Bad Popcorn in Big Buckets(Wansink & Kim, 2005)

AVAILABILITY: eating just because its there

Underestimation of energy content of large portions (Chandon & Wansink, 2007)

Small, medium and large meals were chosen at McDonald’s and Subway and volunteers estimated energy intake.

Greater underestimation of energy intake with larger portions in both restaurant meals

Est

imat

ed e

nerg

y in

take

, kc

al/p

ortio

n

Portion energy intake, kcal/portion

An Optimal Weight Control Diet Satisfies The Three Distinct Neurological Systems That Regulate Feeding Behavior

Hunger-Satiety(1º hypothalmus)

Hedonic Pleasure(1º orbitofrontal cortex)

Reward ( “need”)(1º nucleus accumbens)

Hunger & Satiety Reward & Pleasure

An optimal weight control diet will give a sustainable balance between reward/pleasure and hunger/satiety

Afferent signals (body to brain) report bodily needs to hunger-satiety and reward/pleasure centers:• Vagal nerves from

stomach & lower GI• Gut hormones from

stomach & ileum • Circulating nutrients

(glucose & FFA in blood)

• Fat cell hormones such as leptin

• Post ingestive conditioning (eg dopamine reward in midbrain) anticipates and maintains reward for eating high calorie foods and familiar foods

And trigger the ‘cephalic phase of digestion’ in unconscious lower brain which:• Increases real

metabolic hunger

signals (↓ blood glucose)

• Relaxes stomach muscles (so larger stomach volume,

needs more food for satiety)

• Accelerates GI motility (more rapid digestion speeds return of hunger and desire to eat again sooner

The senses report what’s out there to hunger-satiety and reward/pleasure centers: • Sight • Smell • Taste

internal control

external control

Neurological rather than psychological explanations

What it all means…

• In effect, our environment controls:- our metabolism- our hunger- our synthesis of neurotransmitters such as dopamine that keep us eating- when there is more food we eat more to feel adequately satisfied

• People feel guilty about weight gain, but for the most part we overeat to feel we are eating normally, because environmental control over hunger and metabolism happens in our lower unconscious brain

Explains why an increasingly toxic food environment made us eat an extra 564 kcal/d of HF corn syrup and oil since 1975!

• Accept that the obesity crisis won’t be solved without much more federal government involvement.

• Get economists and nutrition scientists together to work out how you can change the food environment. Introducing healthy choices won’t be enough!

• Think big. This is not just about regulating school food. Could fuel emission standards be a model for restaurants and food companies? Federal junk food taxes? Subsidized weight programs?

• Continue ongoing efforts to eliminate: - false claims of rapid weight loss - food advertisements that encourage overeating

• Would take charge. Diet sensibly. Make their work food environment better for weight control. As parents, get involved in school food.

Consumers

Government

• Would refuse advertising for foods that promote obesity and untested gimmicks and diets falsely implying more weight loss that typically achievable.

Media

In the ideal world…

Individual Energy regulation: influenced by several factors

HUNGER: the need to feel satisfied

AVAILABILITY: eating just because its there

CALORIE DENSITY: what we like most

VARIETY: passive overeating and sensory specific satiety

FAMILIARITY: maintaining established eating habits (just because they are familiar)

Fiber Glycemic Index Protein Volume

  Current Paleolithic Ratio P:C

Folate 0.08 0.12 1.5

Vit. A 2.1 5.7 2.7

Vit. C 24 201 8.4

Vit. E 3.5 10.9 3.1

Iron 4.9 28.5 5.8

Ca 392 653 1.7

Zinc 5.3 14.5 2.7

Fiber (g/d) 15 104 6.9

Western vs. Paleolithic Diet (Eaton et al. 1997)

(mg/d)

Dietary factors thatreduce hunger and/or

increase satiety relativeto energy intake

Hunger: Not All Calories Are Equal

Liquid calories have the oppositeeffect of no satiety despitehigh calories

Effects of a Combined Nutrition and Behavioral Weight Loss Intervention in Worksites

(Salinardi, Batra et al, in preparation)

A RCT of a 6 mo worksite weight loss program was conducted in 4 worksites (2 for profit, 2 non-profit) with 100-500 employees in Greater Boston.

Control sites were wait listed for the program.

Individuals in intervention sites with BMI >25 kg/m2 could sign up for a comprehensive behavioral intervention involving weekly group meetings for 16 weeks and then biweekly meetings for 8 weeks.

14% total employees enrolled and 89% of enrollees completed the 6 month program. Weight loss was significant in both intervention sites.

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Summary

Positive and negative energy balance are different states: easy to be in positive energy balance, hard to be in negative energy balance.

Implication 1: unlikely to resolve the obesity epidemic with community-level prevention measures alone

Implication 2: need greater emphasis on developing effective, sustainable, cost-effective weight loss interventions for the 2/3 population already overweight or obese