Diet and physical activity Flashcards
What is the importance of combining a healthy diet with physical activity for reducing the health risks associated with obesity?
- Obesity is known risk factor for heart disease, stroke, cancer and t2 diabetes
What is the role of diet in providing the body with fuel, how is it stored and how is it metabolised?
First law of Thermodynamics:
Energy cannot be created or destroyed; it can only be converted from one form to another
- Weight loss occurs when energy output exceeds energy intake
-> this is regardless of diet’s macronutrient mixture or time of consumption
- Digesting proteins burns calories compared to carbs, as proteins take more energy to break down
Energy - the ability to perform work
Potential energy (fat)
Kinetic energy (movement)
What are the 3 ways in which diet and physical activity can be used as a weight-management intervention?
- Reduce caloric intake below energy requirements
- Maintain caloric intake and increase energy requirements
- Reduce caloric intake and increase energy requirements
Evaluate the role of soft drinks on level of obesity, and why diet drinks are associated with weight gain
- Dieting alone is not effective
- Most effective are lifestyle changes incorporating physical activity
- Soft drinks most associated with weight gain
- Fructose does not affect leptin or insulin so calories are gained without feeling full or satisfied
- Liver is only organ that can metabolise fructose
-> Excess fructose is stored as fat - not providing any nutritional or energy value - Fructose associated with developing obesity, T2 diabetes + high blood pressure
Diet drinks:
- We have a natural tendency to associate sweet things with providing energy but we lose this tendency when we consume diet drinks
- Taste becomes a poor predictor of calories, so we tend to consume more sugar and become less active
What are the different types of fat and what are the types of food sources that contain the different fats?
Polyunsaturated fats - Omega 3 (fatty fish, walnuts) + monounsaturated fats (olive oil, most nuts) -> liquid at room temp
Saturated fats (meat, butter) -> solid at room temp
Trans fats (cakes, pizza, doughnuts)
How can different types of fat affect HDL and LDL cholesterol?
Polyunsaturated fats (Omega 3 are the best fats, they increase good HDL cholesterol and reduce harmful LDL cholesterol
Monounsaturated + polyunsaturated fats contain lots of good HDL cholesterol
Saturated + trans fats contain bad LDL cholesterol
If we consume a lot of LDL cholesterol, it will accumulate on our arteries + narrow arteries + increase our blood pressure, leading to risks of heart disease, heart attack, risk of stroke
HDL cholesterol regulates the storage and promotes excretion of LDL cholesterol
What are the roles of fats (lipids) in the body and why are they important?
- Main source of energy
- Protects internal organs
- Thermal insulation
- Vitamin carrier and hunger suppressor
Compare and contrast the way Leptin and Ghrelin affect appetite regulation
Leptin:
- Produced by fat cells during digestion
-> the more fat cells, the more leptin
- Monitors body’s fat supplies
- Suppresses appetite via neural signalling
-> signals hypothalamus to increase or suppress hunger based on our fat levels
- Receptor sensitivity declines during pregnancy, hibernation and as a result of obesity
-> when receptor sensitivity declines, Leptin can no longer suppress appetite as the signal is not taking place so hunger will increase
Ghrelin:
- Released by stomach during food deprivation
- Signals PVN to increase appetite
- Nicotine also signals this area
- Damage to PVN will lead to overeating
What is the area of the brain that is involved with leptin, ghrelin and insulin regulation?
Paraventricular nucleus (PVN)
Ventromedial hypothalamic nucleus (VMH) inhibits feeding - damage to this area can lead to overeating + weight gain
How do glucose and insulin interact to provide the body with energy stores
- Most food contains glucose
- Excess glucose is stored in either the liver (as glycogen) or converted to fat
-> glucagon converts glycogen to glucose - High insulin levels deplete glucose which stimulates hunger and increases weight (e.g. hibernation)
- When we are hungry we eat
- Blood glucose increases + insulin release increases
- Insulin helps glucose enter cells so hunger decreases
- Blood glucose declines, insulin release declines
How is the process of glucose + insulin interaction disrupted in T1 and T2 diabetes?
T1 diabetes: Low insulin levels mean little glucose is absorbed into cells, typically leading to weight loss
-> insulin injections
T2 diabetes: Overeating/lack of exercise reduces receptor sensitivity
Critically evaluate the environmental, behavioural and psychological causes of obesity
Environmental:
- Availability of calories we consume (ultra processed food, sugar etc)
-> temptation is there
- Sedentary lifestyles (not enough physical activity)
-> most jobs are sedentary (working from home, sitting at desks etc) - lower levels of PA
Psychological:
- Psychological disorders
-> not strong evidence that they are a major cause of obesity
- Prenatal epigenetic effects (e.g. Dutch Hunger Winter)
-> prenatal environment affected postnatal weight and susceptibility to disease
-> exposure to high fat diet before birth predisposes offspring to increased appetite and body weight - Gene/environment interactions (e.g. Native American Pima of Arizona and Mexico)
-> Evolved, adaptive dietary strategy that due to change in environment led to obesity
Genetics:
- Single gene mutations account for only a small percentage of people with obesity
- But obesity has a high degree of heritability
- Heritability of obesity ranged between 40-80%
Monogenic: high genetic contribution, rare, no environmental influence
Polygenic: modest genetic contribution, common, environment is a key determinant
Describe the brain mechanisms associated with disordered eating habits
Bulimia Nervosa + Anorexia:
- Affects around 1% of pop
- 95% comorbidity with depression
- Associated with increased ghrelin
-> not consuming sufficient calories so body is always hungry + always producing lots ghrelin (more a symptom than a cause)
- Neurochemistry resembles drug addiction
-> eating tasty food stimulate many of the same brain areas as addictive drugs
What is Schrodinger’s argument of psychological entropy and how does interacting with our environment including physical activity reduce internal entropy?
Second law of thermodynamics:
Entropy: An expression of the disorder or randomness of a system
- The total entropy of an isolated system can never decrease over time
-> entropy always increases with time
- Schrodinger argued that living systems survive by reducing their internal entropy
- We can reduce our internal entropy by increasing our interaction with the environment -> by consuming resources (mostly food) from the environment
-> we can use physical activity to reduce our internal entropy (helps us strengthen our bodies, makes us more resilient)
What are some of the benefits of physical activity for improving disease outcomes + alleviating long-term health conditions?
Immune functioning:
- regular exercise reduces risk of chronic metabolic + cardiorespiratory diseases
- inverted J-hypothesis
-> moderate exercise reduced risk of developing infections but paradoxically increases risk in athletes
Obesity:
- reduced visceral fat
- increases HDL + lowers LDL cholesterol
Diabetes:
- increases insulin sensitivity
- reduces blood sugar
Joint health:
- increases bone mineral density
- improved balance, muscle strength + coordination
Cardiovascular disease:
- lower blood pressure
- reduced atherogenesis
- strengthens heart
What are some of the mechanisms that help physical activity to reduce cancer risk?
- Physical activity reduces the risk of developing cancer by 8-25%
- lowers sex hormones
- reduced insulin
- improved immune function
- prevents obesity
- Between 37-49% reduced mortality risk
What is the role of physical activity in improving cognition across the lifespan + what are the mechanisms involved?
- Physical activity prevents cognitive decline, dementia + Alzheimer’s
- Improved cognition and academic achievement in children
Mechanisms:
- increased brain-derived neurotrophic factor (BDNF) + increased hippocampal volume
BDNF -> regulates glucose + energy metabolism and prevents exhaustion of B cells
-> decreased levels of BDNF are associated with depression, anxiety + schizophrenia and diseases such as Parkinson’s disease, Alzheimer’s disease, Huntingdon’s disease etc.
-> BDNF critical for neurogenesis (formation of neurons) + forming new synapses which improves cognitive functioning + reduces stress
-> regulation of cell proliferation, migration, differentiation + death
Evaluate the effectiveness of physical activity with traditional therapies in the treatment of depression + anxiety
Traditional therapies:
- Medication (e.g. Prozac)
- Talking cures (e.g. CBT)
Limitations:
- Medication: side effects
- Talking cures: expensive, time consuming
- Not effective for everyone
Benefits of PA on mental health:
- Reduced stress, allostatic load and HPA axis dysfunction
- improved self-esteem + mood
- Improved sleep quality + duration
- Increased vitality + energy
Benefits of PA on depression:
- Comparable to traditional therapies in clinical populations
-> evidence that exercise is effective treatment for depression, improving depressive symptoms to comparable degree as pharmacotherapy + psychotherapy
- Reduces symptoms in non-clinical populations
-> active people have low rates of depression + reduced depressive symptoms
Benefits of PA on anxiety:
- Similar mechanisms to depression
- PA outperforms traditional therapies in clinical populations
- Lowers risk of anxiety in non-clinical populations
What are the biological mechanisms that drive the process of treating anxiety + depression?
Depression:
Physiological mechanisms:
- Increased norepinephrine
- Increased serotonin
- increased dopamine
- Increased opioids
- Increased hippocampal neurogenesis via BDNF
Anxiety:
- Downregulation of certain serotonin receptors
- B-Endorphin inhibits activation of CNS
- Increased atrial natriuretic peptide
- BDNF/Hippocampus pathways
What are some of the limitations of engaging in PA as a treatment for mental health conditions?
- Poor mental health associated with lack of energy + motivation to engage in PA
- Anxiety may reduce PA e.g. social physique anxiety
Why is calorie restriction without PA largely ineffective as a long-term weight management intervention?
Dieting is largely ineffective
-> most effective are lifestyle changes incorporating PA
- Calorie restriction can decrease metabolism + cause you to lose muscle mass, making it more difficult to maintain weight loss in long term
