Undernutrition Flashcards
What is undernutrition?
Less than adequate energy and/ or protein intake
- Insufficient nutrient intake
- Disordered nutrient uptake/ use
What may cause insufficient nutrient intake?
- Food insecurity/ famine
- Voluntary fasting/ starving
- Anorexia nervosa
- Depression
- Illness
- Medication
Common in elderly and children
What may cause disordered nutrient uptake/ use?
- Digestion, absorption and transport difficulties e.g Coeliac Disease
- Wasting disorders
- Increased metabolic demands
What is a chronic energy deficiency?
- Over a long period
- Low but stable body weight –> in a steady state
- In energy balance but at a low cost
- Several energy saving homeostatic responses to adapt to changes to allow energy balance to be maintained
What is acute energy deficiences?
- Sudden decline body weight –> >10% loss of body weight over 3-6 months
- Often existing disease –> adaptations to conserve energy may not happen
- Energy deficiency + infection/ injury = faster loss of body weight –> due to catabolic response to injury
What happens to energy expenditure during acute critical illness?
Increased BMR
Occurs in patients with
- fractures (depends on number of fractures –> multiple = higher increase), post-operative, cancer, liver disease, sepsis and fever.
The greatest loss is in burns patients - doubling of BMR with 40% burns.
(Some energy savings from being bed bound)
What are the mediators of the acute catabolic response to injury?
Hormones
- Raised Catecholamines and Cortisol
- Promote increase in metabolic rate, nitrogen loss and glucose production
- Early reduction in insulin are later increased as insulin resistance develops
Pro-inflammatory cytokines
- TNFa, IL-I, IL-6
- Stimulate acute phase protein synthesis in liver
- e.g Mobilise clotting factors
What is the body composition changes occur in chronic energy deficiency?
- Reduction of weight, height, BMI, fat mass and fat free mass –> produces considerable energy saving, as less weight means the body is able to adapt to lower energy intake as the demand is lower.
- Viscera: Skeletal muscle ratio is increased –> Skeletal muscle is lost –> has effect on BMR as visceral fat is more metabolically active in resting situations, have a relative impact on energy expenditure
- Usually shorter, indicating chronic nature –> stunted growth especially if occurs from childhood, can continue on to adulthood
- Poor insulation against the cold –> decreased fat mass means there is less fat to insulate. Have a greater vasoconstriction response, susceptible to hypothermia.
What are the energy adaptions from CED to RMR?
Reduced RMR in CED due to
- reductions in body weight (FFM) –> less metabolism occurring in organs and tissues
- possible enhanced metabolic efficiency –> oxygen consumed can produce more ATP?
Keys et al 1950
- 36 individuals, partaking in a political stance against WW2 –> semi-starvation trial
- 24 week starvation period, then re-nourished after
- Idea to understand the impact of WW2 on famine
Results
- BMR decreased by 25% per kg of fat free mass
- Most rapid decline was in the first 2 weeks
What are the energy adaptions from CED to physical activity?
- Likely a decrease in voluntary PA –> behavioural change, do more sedentary activities
- Can be seasonal variation in those people who need to work hard - agricultural labour –> in some areas in certain seasons food is more abundant that in others
- No real evidence of mechanical efficiency –> amount of work per amount of mass
- Ergonomic efficiency –> adjust way of carrying heaving loads
- Reductions in recovery after exercise –> less fit/ have less exercise capacity
Physical, ergonomic and and behavioural
What is the energy adaption from CED to thermogenesis?
Thermic effect of food (TEF)/ diet induced thermogenesis
- Very little data in the area
- Possibility that this is reduced in CED
Response to cold
- Heat loss from less insulation
- Greater vasoconstriction and earlier onset of not shivering thermogenesis to compensate for lack of adipose tissue
- If temp continues to drop there is hypothermia risk
What are the overall energy adaptations to CED?
Negative energy balance
- Increased metabolic efficiency? –> Decreased BMR and thermogenesis –> Lower energy expenditure
- Decreased energy stores –> Lower body size –> Decreased BMR and thermogenesis –> lower cost of activity –> lower energy expenditure
- Decreased physical activity –> lower energy expenditure
Discuss weight changes with negative energy balance
Rapid initial loss
- Water loss associated with depletion of liver and muscle glycogen reserves
Much slower loss
- Energy balance regained at lower body weight
Why?
As less food is eaten there is a decreased energy cost of
- Digestion
- Absorption
- Synthesis of triglyceride reserves and glycogen reserves
- Decreased protein turnover –> protein synthesis more likely to be inhibited/ reduced
As body weight decrease
- BMR decreases
- Decreased cost of physical activity
What regulatory mechanisms behind the energy adaptations to CED?
Adaptations are aimed at maintaining function/ survival
Nervous system
- Reduction of sympathetic nervous system activity with underfeeding –> lower levels of adrenaline, noradrenaline
- Discovered in animal models and short term human studies
Endocrine
- Thyroxine (T3) reduced in starvation –> thyroid hormones are the main hormones in regulating metabolic rate. Less T3 to stimulate metabolism
- Other potential mediators include leptin, insulin, insulin-like growth factor, progesterone
What are the consequences of CED?
Decreased muscle strength and endurance:
- Associated with lower muscle mass
- Also strength is reduced per unit of muscle
- Suggests functional changes in skeletal muscle
- Decline in fast type 2 fibres/ conversion to slow type 1
- Reduction in substrate storage
Reduced immunity:
- Delayed wound healing post op
- Prolonged hospitalisation
- Mortality increases sharply with BMI <16
- Chest infection –> less muscle mass to do the contractile function of breathing
Altered autonomic nervous function:
- Sympathetic nervous system activity decreases
- Parasympathetic nervous system activity increases
- Receptors for neurotransmitters alter in number –> potential cognitive impairment
- Drugs that work on receptor site may need a dose alteration
Psychological:
- Depression
- Anxiety
- Reduced will to recover
- Potential eating disorder risk
