Scientific Inquiry Tied to Genetics, Evolution, and Obesity Module 4.1

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 Advances in nutrition are made using the scientific method. The scientific method uses: an unbiased approach to examine the interaction of food, nutrients and health. is driven/guided by a hypothesis Follows a basic format: Ask a question (define the problem) Form a hypothesis-statement Design an experiment Collect, analyze & interpret the data Generalize & publish the findings Ask another question (the findings generally leads to more questions) The study of health and disease trends and patterns is called epidemiology.

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

Experimental Design A well-conducted experiment requires An Adequate sample size number of subjects used in a study Controls- assures subjects did as requested control group and treatment group comparison of treated and untreated individuals prevention of experimenter bias Psychosomatic Effects effects of the subject’s state of mind on his or her physiology use of placebo in control group Statistical testing – supports measurable data provides statements of probability provides evidence of results

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 and Study Types Case studies- Results from a single person protocol conducted by a medical doctor. Clinical studies- Experimental design with a group of people. Observational or Epidemiology- Population based, retrospective or prospective. Often retrospective (looking back) and are used to assess potential causation in exposure-outcome relationships and therefore influence preventive methods. Intervention trials - Population based, retrospective or prospective. often prospective (looking forward) and are specifically tailored to evaluate direct impacts of treatment or preventive measures on disease. Laboratory experiments - Experimental design with any life form; microorganisms, virus, animals, plants, cell lines, bugs, etc. Testimonials are NOT based on research!!

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 Recommendations 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). American Heart Association as of 7/2016 indicated almost 13 million (16.9%) of U.S. children ages 2 to 19 are obese. Nearly one in three (31.8%) U.S. children (23.9 million) ages 2 to 19 are overweight or obese. More than one-third (about 35%) of U.S. adults are obese (more than 78 million adults).

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

Why is Obesity of Concern? Epidemiological studies have conclusively verified the significant rise in obesity. Why the concern? Raises blood cholesterol and triglyceride levels. Heart disease Lowers "good" HDL cholesterol. HDL cholesterol linked with lower heart disease and stroke risk Hypertension - causes your blood to pumping through the heart and blood vessels with too much force. Over time, consistently high blood pressure tires the heart muscle and can enlarge it. Induces diabetes & cancer - Type 2 diabetes becoming more prevalent in obese adults & children. Obese children are more likely to become obese adults. Type 2 diabetes affects the way your body metabolizes sugar by either resisting or not producing enough insulin Liver/gallbladder disease (overworked due to high fat diets) Arthritis / Hernia / Varicose veins High-risk pregnancy Accidents Depression; low self esteem; decreased longevity, life quality

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%

Behavorial Risk Factor Surveillance System, CDC. 2014