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

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. Presentation Overview

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)

Design the study to test the hypothesis The Scientific Method 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 TheoryScientific Explanation CellThe 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. EvolutionThe 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 PointThere 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 geneHumans 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. GlucostaticBlood 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.

Case studies Clinical studies Intervention trials Epidemiology Laboratory experiments Research Designs

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.

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). Public Recommends

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).

BMIRISK < ≥40 Underweight Normal Overweight Obesity (class I) Obesity (class II) Extreme Obesity BMI BMI= wt(kg)÷[ht(m)]2 BMI HtWt (lbs)

1991 (*BMI  30, or about 30 lbs overweight for 5’4” person) Obesity Trends* Among U.S. Adults BRFSS, 1991, 1999, 2008, and 2010 For updates go to No Data <10% 10%–14% 15%–19% 20%–24% 25%–29% ≥30% 2010

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