1. Scientific Inquiry Tied to Genetics, Evolution, and Obesity
By Jennifer Turley and Joan Thompson
© 2013 Cengage

2. Presentation Overview
The field of nutritional sciences
The process of science
The scientific method
Research/study designs
How dietary recommendations are made
Epidemiological study results reveal an obesity epidemic.

3. Scientific Inquiry
The field of nutrition is based on scientific study that integrates biology, physiology, microbiology, botany, chemistry, genetics and molecular biology.
In order to understand how evidence is produced, it is crucial to understand the basics of scientific inquiry.

4. The Scientific Method Is hypothesis driven Follows a basic format
Ask a question (define the problem)
Form a hypothesis
Design an experiment
Collect, analyze & interpret the data
Generalize & publish the findings
Ask another question (the findings generally leads to more questions)

5. The Scientific Method Design the study to test the hypothesis
A validated hypothesis may lead to a theory such as the theory of evolution or the thrifty gene theory

6. Examples of Theories in Science and Nutrition
Theory
Scientific Explanation
Cell
The cell is the most basic unit of life, organisms are made of one or more cells, and new cells arise from existing cells. Years ago it was hypothesized that humans are born with a certain number of fat cells. Now it is known that fat cells can divide when they have been filled to capacity.
Evolution
The change in heritable genetic composition of a population, such as by gene mutation and as a result of natural selection. There are several theories about how life forms began on earth; the well accepted theory of evolution is one of them.
Set Point
There seems to be a range of body weight that is relatively easy to maintain and is genetically and physiologically controlled. The lower body weight range is more tightly defended to prevent starvation and preserve life.
There are many feedback mechanisms that influence intake and satiety.
Thrifty gene
Humans who efficiently stored food energy as body fat survived tough times during the hunter-gatherer period of human existence. Natural selection of these thrifty genetic traits through evolution may lead to present day obesity when the person lives in a toxic food environment and leads a sedentary lifestyle.
There are many factors involved in survival; energy storage ability is one of them.
Glucostatic
Blood glucose levels affect overall bodyweight; mild hypoglycemia is associated with elevated levels of insulin which inhibits the satiety center and promotes positive energy balance. Normal glycemia results in satiety and better weight control. There are many factors involved in bodyweight control; glycemia is one of them.

7. Research Designs Case studies Clinical studies Intervention trials
Epidemiology
Laboratory experiments
Testimonials are NOT
based on research

8. Study Types
Case: Results from a single person protocol conducted by a medical doctor.
Clinical: Experimental design with a group of people.
Epidemiological & Intervention: Population based, retrospective or prospective.
Laboratory: Experimental design with any life form; microorganisms, virus, animals, plants, cell lines, bugs, etc.

9. Experimental Design things to consider
1. Number of Subjects: is there enough for statistical significance.
2. Duration of the Study: is it long enough for conclusions to be made.
3. Matching Groups: Ethnicity, gender, age, lifestyle, disease.
4. Control Groups: experimental vs placebo.
5. Reproducible Results: can the experiment be repeated and yield the same results.
6. The Treatment Protocol: blind, double blind, crossover.

10. Treatment Protocol
Blind: the subject does not know if they are in the experimental or control group.
Double Blind: the subject and the primary investigator do not know who is in the experimental or control group.
Cross over: each group experiences a period of being on the placebo and experimental drug.
A highly reputable study design is called the double-blind cross over experiment.

11. Public Recommends
Consistent results from multiple credible studies published over many years are used to make dietary recommendations.
A whole body of evidence, collected over many years of experimentation is interpreted by the scientific community to create public recommendations regarding diet and health (disease prevention).

12. Epidemiological study results reveal an obesity epidemic

13. Obesity: An Epidemic
Obesity is body fatness significantly in excess of the level that is consistent with optimal health.
There has been an uncontrolled rise in obesity in the United States over the last 20 years.
Obesity is defined by Body Mass Index (BMI).

14. BMI BMI= wt(kg)÷[ht(m)]2 BMI RISK <18.5 18.5-24.9 25-29.9 30-34.9
≥40
Underweight
Normal
Overweight
Obesity (class I)
Obesity (class II)
Extreme Obesity
BMI
BMI= wt(kg)÷[ht(m)]2
BMI 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Ht
Wt (lbs) 60 97
102
107
112
118
123
128
133
138
143
148
153
158
163
168
174
179 61
100
106
111
116
122
127
132
137
164
169
180
185 62
104
109
115
120
126
131
136
142
147
175
186
191 63
113
124
130
135
141
146
152
197 64
110
134
140
145
151
157
192
204 65
114
144
150
156
162
198
210 66
155
161
167
173
216 67
121
159
166
172
178
211
217
223 68
125
171
177
184
190
203
230 69
149
176
182
189
196
209
236 70
139
160
181
188
195
202
222
229
243 71
165
193
200
208
215
250 72
154
199
206
213
221
228
235
242
258 73
212
219
227
257
265 74
194
218
225
233
241
249
256
264
272 75
224
232
240
248
279

15. Obesity Trends* Among U.S. Adults BRFSS, 1991, 1999, 2008, and 2010
(*BMI 30, or about 30 lbs overweight for 5’4” person)
1991
1999
For updates go to
2008
2010
No Data <10% %–14% %–19% %–24% %–29% ≥30%

16. Why is Obesity of Concern? Increased risk for chronic diseases
Type 2 diabetes
Type 2 diabetes is becoming more prevalent in obese adults & children.
Obese children are more likely to become obese adults.
The onset of Type 2 diabetes is preventable by diet, exercise & a good weight control program.

17. Why is Obesity of Concern? Increased risk for chronic diseases
Type 2 diabetes
Heart disease & Cancer
Liver/gallbladder disease
Arthritis
High-risk pregnancy
Hernia & Varicose veins
Accidents
Depression & Low self esteem

18. Why is Obesity of Concern? Increased risk for medical conditions
High blood pressure (hypertension)
High blood cholesterol and triglycerides
High blood sugar
Overall obesity leads to decreased longevity and decreased quality of life

19. Summary
Nutrition has relied upon scientific study to understand the relationships between diet and disease.
Data synthesis from multiple study types (laboratory, case study, & epidemiology).
Data synthesis across numerous disciplines (physiology, anatomy, chemistry, immunology, virology, etc) over time.
With consistent results have helped answer questions pertaining to human health.
Epidemiological study results have verified the obesity epidemic.
Obesity increases the risk for many chronic diseases and medical conditions.
References for this presentation are the same as those for this topic found in module 4 of the textbook