Lecture 14 Flashcards
(22 cards)
What is a typical warm weather hunter gatherer’s diet?
studies suggest that plants constitute a much higher contribution to the diet- 65% plants and 35% animal products
How does long distance running play a key role in natural human nutrition?
A large number of physical and physiological attributes arose from powerful selective pressure for long distance, endurance running to facilitate large animal hunts
What variety do humans have for diet?
humans have an incredible capacity for dietary variation. From totally plant-based to over 90% meat in some arctic people
What does the variability present?
This variability in human diet is both intriguing and problematic for dieting
What is the weight maintained feature in the “energy balance” model of body mass?
Isocaloric balance: Energy in= energy out
What is the weight loss feature in the “energy balance” model of body mass?
Negative caloric balance: energy in < energy out
What is the weight gain feature in the “energy balance” model of body mass?
Positive caloric balance: energy in > energy out
Does it matter what kind of foods compose the calories?
Yes, the type of foods one eats is important. 100 calories from an apple and 100 calories from a soft drink is not equal.
What is the hypothesis that time of eating and not eating are important in body mass?
Intermittent fasting and time restricted feeding; basic idea- daily eating is punctuated by a period of no eating, typically between 12 to 16 hours. Many variations
- Idea of “energy balance”- by restricting the time you eat to a limited window-> you restrict the # calories you consume per day
What was the classic S Panda study of time-restricted feeding?
He used mice in 4 groups- normal (N) diet or a high fat (F) diet, ad libitum (A) or for an 8 hr time window (T)
What were S Panda’s results?
All mice ate the same amount of food per day. However, FA group gained body weight and had metabolic disease due to obesity
Biochemically, why is a low carbohydrate diet ketogenic?
Limiting carbohydrate calories causes a shift to fat usage that mobilizes fat stores, lowers blood sugar, and induces ketogenic state
- Fat is used as the primary fuel in the liver to drive glucose production
What are the basic features of the gut microbiome (GM)?
- Between 500-1000 species of bacteria live in the human gut. There are about 10^14 total bacteria in the gut
- Bacteria, the main types of microorganisms, together w/ archaea, fungi, viruses, and protozoans make up the GM
- Intestinal microbial community counts more than 100 trillion microbial cells (4 x 10^13)
- At least 2 million non-redundant genes
- Highly diverse
- Highly dynamic
What makes the human GM dynamic?
Alterations during human life cycle
What makes the human GM diverse?
It is highly personalized; differing microbiota between individuals
What makes the human GM dense?
Intestinal microbial community that inhabits the human gut counts more than 100 trillion microbial cells
What are the early studies of germ-free vs normal mice and the effects on body weight?
Germ-free, meaning no microbiome, mice were unable to grow to full adult weight compared to those allowed to have a normal microbiome (CONV-D) or those who had one added after adulthood (CONV-R)
What is the energy harvesting model of GM action?
GM helps harvest nutrients b/c of the many bacteria and organisms processing the food and generating small molecules
What is the importance of SCFAs in GM action both as calories source and physiological modulators?
Calories source: some people produce more short chain fatty acids which produces more calories-> more energy input -> person has higher fat storage (more weight) Physiological: - Cell signaling - Release of gut hormones - Immune cell function - CNS appetite control
What were the findings in the obesogenic microbiome studies of twin human GMs in mice?
The GM affected the way the mice processed and stored energy; obese twin donors gained weight while all lean twins did not
What were the findings in the studies on fiber-improvement of glucose tolerance and the role of GM?
- The BKB (high fiber) responders develop a higher ratio of Pevotella to Bacteriodes in their gut microbiomes in response to the BKB bread in the diet
- Only the post BKB microbiomes from the responders caused improved glucose tolerance in the recipient mice due to the prevotella/bacteroids ratio
What was the hypothesis and findings of the studies on GM role in adipose conversion caused by Intermittent fasting (IF)?
Findings:
- The IF (EODF) mice showed significantly better glucose tolerance and shift toward beneficial brown adipose tissue as well as less total fat mass
- The model derived from these studies is that IF causes the change in the microbiome that produce metabolites (acetate and lactate) that change BAT ratio and energy metabolism
Hypothesis: IF promotes white adipose growing and decreases obesity by shaping the gut microbiota
