Appetite Regulation and Exercise

Introduction

  • Focus on measuring appetite, gastrointestinal hormones, and data in publication forms.
  • Gastrointestinal system as the "second brain" – historically regulated appetite before brain development.
  • Body's control via appetite regulation and metabolic processes.

Focus Areas

  • Exercise effects on gastric emptying, appetite, and the gastrointestinal system.
  • Using exercise as an acute stimulus to understand the gastrointestinal system's response and broader human body response.

Learning Objectives

  • Describe energy balance in relation to weight gain/loss.
  • Explain why energy in vs. energy out is not a simple concept, especially in obesity.
  • Outline methods for measuring gastric emptying, considering cost implications and benefits in applied settings.
  • Understand how to measure the gastrointestinal system's response in the stomach.
  • Explain visual analogue scales and their role in psychological measurement of appetite perception, linking it to physiological measurements (hormones).
  • Identify hormones that regulate food intake/appetite.
  • Understand exercise as an acute stimulus causing changes in the gastrointestinal system.

Key Terms

  • 13C isotope: Used to measure gastric emptying.
  • Exercise intensity: Affects gastric emptying.
  • Pyloric sphincter: Regulates movement of food/liquids from the stomach to the small intestine.
  • GLP-1 and Ghrelin: Hormones regulating appetite responses and signaling between the gastrointestinal system and the brain.
  • Energy intake and macronutrients: Protein, carbohydrate, and fat.
  • Satiety: Appetite regulation.

Relevance of Appetite Regulation Research

  • Impact on obesity and weight management.
  • Global rise of overweight, obese, and morbidly obese populations.
  • Sugar tax initiatives to control "wasted calories."
  • Understanding appetite regulation in gaining weight (appetite signal leads to food intake and excess energy).
  • Metabolizing food, blood glucose changes, triglycerides, cholesterol, and non-vice fatty acids being released into our bloodstream.
  • NHS pressures due to obesity-related conditions.

Energy Balance

  • Weight Loss: Energy out > Energy in; utilizing adipose tissue for energy.
  • Weight Maintenance: Energy in = Energy out.
  • Weight Gain: Energy in > Energy out.
  • Short-term weight gain from exercise due to increased muscle mass, but long-term metabolic adaptation leads to weight loss.

Metabolic Systems

  • Diet (food) is broken down into macronutrients (fats, carbohydrates, protein).
  • Digestion: Food is broken down into smaller molecules, absorbed through the small intestines into the bloodstream.
  • Metabolic process: Energy particles are metabolized.
  • Different energy streams: fats, carbohydrates and protein.
  • Carbohydrate metabolism: broken down to glucose. Brain uses 40% of all carbohydrate intake
  • Adipose tissue: storage of energy when starving.
  • Energy regulation requires understanding movement between metabolic systems.
  • Covered in level five, you do metabolic biochemistry with Paul, and you will start going into a much more detail about these things that he would have spoke about, like gluconeogenesis, gluconeogenesis, the way we break down glucose, restore it, release it again.
  • When we've actually started to look at the hormones that are on here, that down the bottom here like GLP-1, K, ghrelin, some of these signal through that vagus nerve that connects from the stomach directly to the brain. That causes functional change to happen.

Relevance to Neuroscience

  • Hormones (GLP-1, ghrelin, etc.) signal through the vagus nerve from the stomach to the brain.
  • Functional changes occur due to this signaling.
  • Connect psychological feelings of appetite with physiological events.
  • Read the suggested paper to understand how hormones signal to different brain parts, linking to appetite changes, metabolic processes, and weight management.

Digestive System

  • Purpose: allow food to enter, break down, extract energy/nutrients, and expel waste.
  • Enter-exit system with no storage; nutrients are absorbed into the bloodstream.

Phases of the Gastrointestinal System

  • Cephalic Phase: Perception via sight, smell, taste of food.
  • Gastric Phase: Digestion in the stomach.
  • Intestinal Phase: Small intestines (macronutrient digestion/absorption). Large intestines (microbiome and energy release).

Stomach Structure

  • Fundus (top).
  • Main body.
  • Pyloric atrium (bottom).
  • Pyloric sphincter prevents food from leaving the stomach and entering small intestines.
  • Food held in the stomach for up to four hours.
  • Continuous mixing process.

Gastric Emptying

  • Fluids leaving the stomach and entering the intestines.
  • Pyloric sphincter controls fluid movement between the stomach and small intestines.
  • Regulated by the vagus nerve (ghrelin and GLP-1).
  • Pyloric opens and some of the liquid is forced through into our small intestine.

Gastrointestinal Process

  • Food entering the stomach releases gastrin, hydrochloric acid, enzymes, and peptides to break down food.
  • Food stimulates the cell wall and release of bile (from the liver) and digestive enzymes (from the pancreas) into the small intestines.
  • Nutrients are absorbed. Insulin and glucagon are released, thus helping regulate and transport substances around the body.

Factors Affecting Gastric Emptying

  • Energy density of food.
  • Food consistency (solid or liquid).
  • Volume of food.
  • Empty stomach: Ghrelin is high.
  • Stomach fills up, it reduces ghrelin that leads to GLP-1 being released.

Measuring Gastric Emptying

  • Radio isotope imaging (historical).
  • MRI (magnetic imaging).
  • Ultrasound (volume changes).
  • Gastric aspiration technique (removing liquid from the stomach).
  • Breath test method using 13C isotope (measuring carbon 12/carbon 13 ratio in breath).

Gastric Aspiration Technique

  • Swallowing a tube through the nose or mouth.
  • Allows measurement of liquid leaving the stomach.
  • Can test perception with different food solutions.
  • Removes cephalic phase.

Breath Test

  • Ingest sodium acetate with carbon-13.
  • Digest food and absorb it into the bloodstream.
  • Metabolize isotope in the liver.
  • Measure carbon isotope ratio through breath samples.

Pros and Cons of Measurement Techniques

  • Gastric aspiration: Directly measures food/liquid but is invasive and has limited meal types.
  • Breath test: Non-invasive and can measure liquid/solids, but provides an indirect measurement of gastric emptying.
  • MRI and ultrasound: Improve imaging, but can be expensive and not as applicable in applied settings.

Visual Analogue Scales

  • Questionnaire to measure appetite perception.
  • Six defined questions (hunger, fullness, etc.).
  • 100mm scale; participants mark their perception.
  • Transformed into numerical data for statistical analysis.
  • Numerical scale with defined scaling category.

Problems with the Scale

  • Cognitive: Is it valid or reliable.
  • What other things could be used, such as hormones.

Hormones

  • Match appetite perception to physiological markers (hormones).
  • Hormones such as state ghrelin, GLP-1, PYY, insulin, secretin, and CCK may show alignment.
  • Appetite scores are easy to use alone but subjective.
  • Physiological markers can be manipulated to show how brain function is signals.

Main Hormones

  • Ghrelin: Peptide appetite regulation hormone, released from the stomach and circulates the only known stimulator of appetite.
  • PYY and GLP-1: When they are high, we are specifically full.
  • Follow-on is exercise affect gastrointestinal function.

Exercise and Gastrointestinal Function

  • Review of studies on exercise intensity and gastric emptying.
  • Exercise has various intensities L, R and H.

Supervisor's Paper (2013)

  • Effects of exercise intensity on gastric emptying.
  • Gastric aspiration technique was used to measure gastric emptying.
  • Averages are shown what can be seen. When moved over there a different response in high low and breast, individually.
  • Higher VO2 max basically come back to the higher fitness level.
  • Shows that blood leaves the gastrointestinal system, and diverted to other parts of our body is systems (the working muscle).

Follow-Up Study

  • Ingesting fluids with whey protein or multi texture (carbohydrate).
  • Two trials crossover.
  • Protein vs. carbohydrates.
  • Looking at differences in gastric emptying.
  • Gastric 13 breath test.
  • The protein peaks a lot later on, at about 60minutes.
  • Someone who is fit exercising continuously; they see the similar results between that of people who are athletic.
  • The stomach just like a muscle, just like a bone, just like a nerve, has the ability to be trained or certainly trained, maybe to sense different nutrientsMaybe carbohydrate is sensed with the oral receptors telling the brain that carbohydrates that that brain that carbohydrates coming into metabolites.
  • Rinsed carbohydrate solution or water in their mouth. The participants who rinse with carbohydrate significantly, regularly across a number of different papers and students institutions share that people can perform for longer when they rinse with carbohydrate, almost the receptor telling the brain that carbohydrates is coming in keep going. You've got that energy coming in.

My Research Entry Point

  • Limited exercise, gastric emptying and hormone regulation.