Diet & Weight Management Flashcards
Obesity
- ABS
- Factors related to weight management
- Energy and Macronutrient intake
ABS
- 2016: Over 60% of Australians are overweight or obese.
- 2017-2018: Two thirds (67.0%) of Australian adults were overweight or obese (12.5 million people)
* National Health Survey 2017-18
+ Almost 24.9% of children aged 5-17 years were overweight or obese (17% overweight and 8.1% obese)
Factors related to weigh management
- 25% Genetics
- 30% Culture
- 45% Non-transmissible
Energy and Macronutrient
- Negative energy balance = Weight loss
Macronutrient intake
- Excess CHO & Protein
- Alterations in oxidative Rate
- Sociocultural & socioeconomic factors
Excess CHO & Protein Intake
- de novo lipogenesis: The biochemical process of synthesising fatty acids from acetyl CoA subunits that are produced from a number of different pathways within the cell, most commonly CHO catabolism
- Converted to fat? Yes but not the primary fate of excess CHO and protein
Alterations in Oxidation Rate
- Excess amounts of CHO and protein -> ↑ Oxidation rates (primarily)
- FAT? - Oxidations rates do not increase immediately
- …Likely stored as adipose tissue
Sociocultural & Socioeconomic Factors
- Low socioeconomic classes:
- ↑ Fat intake ↓ CHO intake
- Cultural differences - different consumption of CHO, fats and protein
Regulation of Appetite
- Hormones & other factors
Exercise and appetite
Ghrelin
- Stimulates appetite
- Increases before a meal
- Returns to baseline values after meal
Leptin & Insulin
- Influence how much food is eaten
- Satiety hormones
- Can inhibit eating habits
Other factors that influence appetite
- Taste of food, smell of food & nutrients
- Memory - time of day social situation
- Stress
- Exercise physical activity
Satiety - inhibition of eating following a meal, is measured by both
- The interval between meals
- The amount consumed when food is next offered
- HYPOTHALAMIC region of the brain plays a key role in the central regulation of eating behaviour in humans
- Monitoring
- Processing
- Responding to peripheral signals
- Generated mostly in by the GI but also by the pancreas and adipose tissue
Exercise and Appetite
- Intensity – 70% VO2 max (appetite suppressed)
- Duration – 60 mins or more (appetite suppressed)
- Mode - debate, some evidence that different modes affect appetite differently
- Individual appetite responses to exercise vary
Weight Loss
- Methods
- A calorie is a calorie
- Dietary method
- Exercise
- Surgical procedures
- Pharmacological
A calorie is a calorie (4.184 kJ)
- But . . . Calories from different food sources can have a markedly different effect on hunger, hormone, energy expenditure and the brain regions that control food intake…
1. The metabolic pathways for protein is less efficient then the metabolic pathways for CHO and fat
2. Protein reduces appetite more effectively, which results in reduced energy intake (fuller for longer)
3. Different simple sugars are metabolised differently and have different effects on appetite
4. Refined CHO leads to faster and bigger spike in blood sugar which leads to cravings and increased food intake
5. Different foods have different effects on satiety
Energy Restriction
Energy restriction
- Low fat diets
- Increased CHO -> Increased glycogen stores & better recovery (athletes)
- Fat is energy dense
- Fat increases the desire to eat
- Fat is less satiating than protein or CHO
- Fat store efficiently requires little energy for digestion
- Fat intakes does not immediately increase fat oxidation
- High protein
- ↑ Protein in diet from 10-15% to 30%
- Protein supresses appetite – high satiety
- Large thermic effect
- ↓ Fat
- Increase in RMR
- Low CHO diets
- Decrease in CHO (lower insulin level, promotes lipolysis) = Fat oxidation ((Assumption))
- If CHO is restricted to < 20 g/day, ketone body production will increase
- Low CHO linked to better satiety (but likely due to the increase in protein intake)
- No more effective then a well balanced, energy restricted diet
MOST FAVOURED IS LOW FAT DIET
Energy Intake Considerations
- Reduction in total energy expenditure
- ↓ muscle mass
- Protein intake important
- When choosing a diet maintaining muscle mass should be considered
Weight loss
- Metabolic adaptation (adaptive thermogenesis)
- Practicalities of weight loss for athletes
- Energy Density (e.g. % contribution of macronutrients)
Metabolic adaptation (adaptive thermogenesis)
- Response to low energy intake
- ↓ resting metabolic rate over time
- ↓ lean body mass over time, further reduce resting metabolic rate
- …failure to continue to lose weight over prolonged periods of time
Practicalities of weight loss for athletes
Common mistakes
- Trying to lose weight too rapidly
* Glycogen depletion
* Substantial loss of body water
* Reduction in body protein stores
- Trying to lose weight during the competitive phase of the season
- Not eating breakfast or lunch
- Taking in too little CHO
Energy Density (e.g. % contribution of macronutrients)
- Energy density is a major contributor to energy intake
- ↑ energy density = ↑ energy intake
Eating Disorders
- Classification of eating disorders
- Type of eating disorders
- Prevalence in athletic populations
- Eating disorders characterized by gross disturbances of eating behaviours.
- Detrimental effects on sports performance and damaging, long-lasting effects on health and can even be fatal
Classification of eating disorders
- Anorexia nervosa:
- Anorexia athletica
- Bulimia nervosa
- Eating disorders not otherwise specified (EDNOS)
Type of eating disorders
- Eating behaviour can be considered as a spectrum ranging from HEALTHY EATING to overeating in one direction and clinical eating disorders in the other
- Primary concern is energy availability and its specific reference to the athletic population and their desire to make weight in a specific event
Prevalence in athletic populations
- Highest prevalence is reported in gymnasts
Eat Disorders
- Risk Factors
- Health Risks
Risk Factors
- Gender
- Dieting
- Personality
- Exercise dependence
- Type of sport
Health Risk
- Psychological mood states
- Depression
- Fatigue
- Anxiety
- Anger
- Irritability - Growth and maturation
- Stunted growth in adolescent athletes may occur during prolonged periods of inadequate energy, protein, and micronutrient intake.
- Delayed puberty onset
- Poor bone development can lead to increased susceptibility to fractures and problems - Reproductive Function
- Menstrual irregularity, which may be followed by amenorrhea and absence of ovulation
- In this state, the person is infertile, and her endocrine status is akin to that of a postmenopausal woman (low progesterone levels) - Osteoporosis
- Amenorrhea- Ovarian steroid hormones facilitate calcium uptake into bone and inhibit bone resorption
- Can occur despite the fact that load-bearing physical activity induces greater bone-mineral density (BMD).
Eating Disorders and Sport Performance
- Eating stages of dieting
- Early stages of weight loss
- Dehydration
Eating stages of dieting:
- Body adapts
- Uses up stored fat and certain minerals (e.g., iron) and vitamins.
Early stages of weight loss:
- Performance may transiently improve, but
- Endurance performance is likely to deteriorate
- Liver and muscle glycogen levels are low
- Dehydrated
- Anaemic (i.e., the blood haemoglobin concentration falls below normal).
Dehydration
- Common in anorexia nervosa and bulimia nervosa:
* Reduced plasma volume:
+ Impairs thermoregulation during exercise,
* Electrolyte disturbances are also likely to be detrimental to muscle function, and with time, a loss of lean body (muscle) mass will reduce strength and power.
Female Athlete Triad
Eating Disorders
- Anorexia & Bulimia
Amenorrhea
- Irregular mensural cycles
Osteoporosis
- Bone mineral density issues & osteoporosis
