The Silent Manipulator: Protein and the Burden of Obesity in Australia

1

David Raubenheimer Leonard P Ullman Chair of Nutritional Ecology

Faculty of Vet Science | School of Biological Science | Charles Perkins Centre

Nutritional Ecology is ….

• Ecological / evolutionary approach to nutrition

- focus on how nutrition mediates the relationship between animal & environment

- to determine health and wellbeing

Animal Biology

Environment

NUTRITION

health lifespan reproduction etc.

health lifespan reproduction etc.

health lifespan reproduction etc.

Aims for the talk

NUTRITIONAL GEOMETRY

Animal Biology

Environment

NUTRITION

ECONOMIC$

HUMAN APPETITE

OBESITY

• Introduce Nutritional Geometry: approach for studying these interactions

• Show how it has been used to understand:

1.

2.

3. 4.

Carb

ohyd

rate

Protein

excess C

deficit P

• Nutrient requirements

• Foods

• Feeding

- nutritionally balanced foods

- nutritionally imbalanced foods

• The challenge of dietary imbalance

Nutrient space

1) Nutritional Geometry: brief intro

Carb

ohyd

rate

Protein

prioritise C

prioritise P

• Measuring how appetite responds to dietary imbalance

e.g.

life

span

- or contour plot

Protein C

arbo

hydr

ate

- response surface

• Consequences

• How does the human appetite respond to dietary imbalance?

2) Human appetite

?

- humans prioritise P over F + C

• Meta analysis: 26 published trials

model

Gosby et al. (2013) Obesity reviews.

• Experiments in Oxford, Sydney & Jamaica

prioritise P

• Can protein prioritisation help understand the global rise in obesity? Source: Australian Institute of H

ealth and Welfare

3) Obesity

Australia 1980-2008

Protein

Car

bohy

drat

e +

fat

14% P 12.5% P (1.5%)

- a small change in % P in foods will result in a large change in the amount Carbs + Fat eaten

- for example, a 1.5% decrease in % P

14% increase in C + F eaten

-> Called the “Protein Leverage Hypothesis” (PLH)

- could this help explain the obesity epidemic?

• Very likely:

0 10 20 30 40 50 600

20

40

60

80

Energy intake (kj/day)

Protein (% kj)

Fat

(% k

j)

5000

600

0

700

0

800

0

900

0 1

0000

11000 [0]

[20]

[40] [60]

(10:30:60)

1) Energy intake increases with decreasing %P

Two predictions of PLH

- Yes!

Prediction 2) Dietary % P has decreased with the rise in obesity

Data: FAO

STAT 2010 - e.g. Australia

year

Prot

ein

(% e

nerg

y)

- Yes!

4) Economics

• If we prioritise protein, why do we select low-P diets?

?

Source: Australian Institute of Health and W

elfare

• A clue: obesity is more prevalent among low-income groups

- suggests economics might drive the consumption of low-P diets

0 10 20 30 400

20

40

60

80

100

Protein g/100g

Fat +

car

bohy

drat

e g/

100g

0.6

0.8

1

1.2

1.4

1

.6

1.8

2

2.2

1) Protein is more expensive than fats and carbs

$/100g

Brooks et al. (2009) Obesity reviews.

Three predictions

- 106 supermarket foods

- price increases with % P

- not with fats & carbs

• Test

• Result

- compared the separate contributions to the price of each g of Pro, Fat and Car

- suggests an economic incentive to eat low P foods

• Conclude cheap expensive

cheap

Prediction 2). Low SES groups eat low-protein diets

- 14 diet surveys of low SES indigenous Australian communities

- most have low % P relative to recommended range

• Aboriginal study

• Compared with Australian recommendations (AMDR)

[With Aboriginal Nutrition Project Node]

Prediction 3). Low protein diets are associated with high energy intake

- yes!

CONCLUSIONS

Economic pressure

Reduced dietary % protein

Increased energy intake

Obesity

Obesity as an issue of “nutrient security”

PROTEIN LEVERAGE