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

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.

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.

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)

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

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.

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

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.

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.

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.

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).

Epidemiological study results reveal an obesity epidemic

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).

BMI BMI= wt(kg)÷[ht(m)]2 BMI RISK <18.5 18.5-24.9 25-29.9 30-34.9 35-39.9 ≥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

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 http://www.cdc.gov/nccdphp/dnpa/obesity/trend/maps/ 2008 2010 No Data <10% 10%–14% 15%–19% 20%–24% 25%–29% ≥30%

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.

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

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

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