Week 4(1) - Energy balance and health

Question 1

Obesity

Answer 1

Excess accumulation of body energy, in the form of fat (adipose tissue)

Question 2

Types of adipose tissue:

Answer 2

• Subcutaneous adipose tissue: found just below the skin (e.g., gluteal-femoral region – thighs and hips)
• Generally considered neutral or protective. Acts as a metabolic sink for safely string excess energy from the diet. If there is excess energy these fat stores will become saturated and leak out into other stores e.g., visceral
• Visceral adipose tissue: accumulation is a major risk factor for cardiometabolic diseases
• Located deep within the abdominal cavity. Can lead to ectopic fat deposition (e.g., fat in heart, liver, skeletal muscle)

Question 3

Co-morbidities associated with overweight and obesity

Answer 3

• Hypertension
• T2DM
• Dyslipidaemia (abnormal levels of lipids in the blood)
• Cancer risk (breast cancer and bowel cancer most common)
• Mood disorders
• Heart disease
• Reproductive disorders
• Liver disease

Question 4

Reasons Lower BMI cut-off points for Asian populations (compared to White European):

Answer 4

• Asians often have higher body fat percentage at lower BMI
• Increased visceral fat at lower overall body fat levels
• Asian population experience higher risk of obesity related illnesses at lower BMI cut off points

Question 5

Relationship between BMI and Mortality

Answer 5

As BMI increases (from normal weight) there is a dramatic increase in mortality risk
For a male, the Nadir point (optimal BMI) is 22-23.4kg/m2
For a female, the Nadir point is 22-23.4kg/m2
Mortality risk is linked to abdominal/ visceral fat deposition – A more pear shaped fat disruption is less harmful – lower mortality risk (even when classified as overweight)

Question 6

BMI advantages:

Answer 6

• Simple, inexpensive and non-invasive tool
• High BMI is an important risk factor for CVD and T2D
• Good tool for tracking and identifying population trends- comparisons across time, countries, population subgroups etc.

Question 7

BMI disadvantages:

Answer 7

• Surrogate measure of body fatness
• Age (older adults have more body fat than younger adults at the same BMI), sex (females have more body fat than males with an equivalent BMI), ethnicity, and muscle mass can influence BMI interpretation
• Does not distinguish between excess fat, muscle or bone mass
• Does not provide indication of body fat distribution - health risks of obesity are related to body fat distribution (particularly excess abdominal fat)

DEXA scan = an accurate way to determine body fat distribution

Question 8

Significance of weight circumference and IAA:

Answer 8

• Intra-abdominal adiposity (IAA – fat that lines the internal organs in the abdominal cavity) is closely correlated with abdominal obesity
• To assess IAA, the simplest measure of abdominal obesity is waist circumference, which is strongly correlated with direct measurement of IAA by CT scan or MRI, considered to be the gold standard.
• As waist circumference increases, so does intra-abdominal adiposity
• CT scan is very expensive – not appropriate for routine use
• Waist circumference may therefore be a useful proxy for measuring IAA
• IAA is measured by CT scan and waist circumference

Question 10

Food processing spectrum as defined by the NOVA diet classification system -
classifies food according to the nature of processing (ignores the nutritional content of foods)

Answer 10

Group 1) Unprocessed or minimally processed foods: e.g., fresh, dry, or frozen veg or fruit, grains, legumes, meat, fish, eggs, nuts and seeds
- Processing includes removal of inedible/ unwanted parts
- Does not add substances to the original food
Group 2) Processed Culinary ingredients: e.g., plant oils (olive and coconut oil), animals fats (cream, butter, lard), maple syrup, sugar, honey salt.
- Substances derived from group 1 foods or from nature by processes including pressing, refining, grinding, milling and drying
Group 3) Processed foods: e.g., canned/ pickled vegs, meat, fish, or fruit, artisanal bread, cheese, salted meats, wine, beer and cider
- Processing of foods from group 1 or 2 with the addition of oil, salt or sugar by means of canning, pickling, smoking, curing or fermentation.
Group 4) Ultra-processed foods: e.g., sugar sweetened beverages, sweet and Savoury packaged snacks, reconstituted meat products, pre-prepared frozen dishes, canned/ instant soups, chicken nuggets, ice-ream
- Formulated made from a series of processes including extraction and chemical modification
- Includes very little intact group 1 foods
- Cheap industrial sources of dietary energy
- Often contain additives

Question 11

UK national diet and nutrition survey (2008-2014): Contribution of NOVA groups to energy intake (Rauber et al 2018):

Answer 11

• ~ 30% from unprocessed or minimally processed foods (NOVA 1)
• ~ 4% from culinary ingredients (NOVA 2)
• ~ 9% from processed foods (NOVA 3)
• ~ 57% from ultra-processed foods (NOVA 4)

Question 12

Hall et al (2019) investigate the causal role UPFs on energy intake and body weight change

Answer 12

The ultra-processed diet caused increased ad libitum energy intake and weight gain despite being matched to the unprocessed diet for presented calories, sugar, fat, sodium, fibre and macronutrients.
- Ultra-processed diet significantly increased energy intake (~500 kcal/ day more)
- Faster eating rate for ultra processed meals – higher eating rate can result in overall increased energy intake – UPFs industrially produced to be softer and easier to swallow
- Ultra-processed diet: +0.4 ± 0.1 kg body mass (significant body mass increase)
- Unprocessed diet: -0.3 ± 0.1 kg body mass (lost weight on average)

Question 13

Appetite response to UPFs:

Answer 13

• PYY (an ‘appetite-suppressing’ hormone) increased during the unprocessed diet vs. baseline and the ultra-processed diet.
• Ghrelin (a ‘hunger’ hormone) was decreased during the unprocessed diet vs. baseline.
• Suggests there me be a relationship between the structure of food and how it impacts energy intake and appetite response