NFS284 Chapter 7 – Energy balance and weight management
If BMI is too high or too low, then increased risk of mortality.
We are seeing this globally, instead of just being a characteristic of developed worlds. This
emphasizes the fact that obesity (BMI > 25) is a global problem.
The relationship between body weight and various risk factors for health. These risks to heatlh
all increase as body weight increases.
Lung cancer is a consequence of cigarette smoking than nutrition. Prostate cancer doesn't have as
strong of an association with obesity in terms of developing the disease, compared to the other
The mutations change the cell in a number of different ways. They cause de-differentiation of
cells and cells become proliferative (rapidly dividing). A normal cell has a stop signal, which are
lost in the transition from a normal to a cancerous cell.
If the cell cannot repair its own DNA, it will induce cell death. It will kill itself rather than
perpetuate damaged DNA. This is how a normal cell behaves, but a cancer cell keeps growing.
The cell tends to break through the local environment (e.g., basement membrane). Tumors are
able to secrete proteins that dissolve the barrier very readily. The cells can go into circulation.
Only 1 in 1000 cells that go into circulation actually develop into tumors in other parts of the
What is the link between obesity and cancer? There are two link: (1) Some of the things in our
diet may be carcinogenic and (2) Different diets promote cell proliferation. Colon cancer and
breast cancer relate to how changes in metabolism during obesity promote the development of
growth factors. Dietary conditions can change the level of SHBG. You want SHBG to be as high as possible
from the point of view of breast cancer prevention.
Obesity increases the risk of insulin resistance. FFA are very ready source of energy for the
muscle. The muscle becomes lazy at taking up glucose, called insulin resistance. The pancreas
has to secrete more insulin to maintain to move the glucose transporters to the surface of the cell
and to maintain normal blood glucose levels.
Adipose tissue is a source of estrogen synthesis.
Free estrogen is circulating in the blood and readily taken up by breast cancer cells.
Observational studies only show association. The more observational studies are repeated and
the more consistent the observation, the more likely the association may have a causal link. One
of the benefits of an observational study is that it can be conducted for a longer period of time to
be able to measure a disease outcome.
Intervention trials tend to support this data but can't measure disease outcome. You can use
surrogate/intermediate markers of disease. You can biopsy colon tissue and measure proliferation
rates in different cells from individuals who have different BMI or consume different diets.
30% increase in risk with an increase in BMI.
Gall stones form in the narrow ducts that lead from the gall bladder to the liver or to the
intestinal tract. Usually treated by the removal of the gall bladder.
Unhealthy body weight is associated with increased health risk.
Weight stigmatization. Slide 24
Most people are in positive energy balance. The positive energy balance is very small and the
weight gain is very gradual.
All energy expenditure in the body is cellular metabolism.
ATP is used for basal metabolism, which is needed to stay alive.
The amount of energy expended per day. It is a daily energy use. It is called a rate because it is
per unit time. The basal metabolic rate decreases with weight loss because body size is getting
smaller, but our physiology is good at detecting weight loss. It interprets weight loss as
starvation, so it downregulates energy expenditure (e.g., conserve body energy). The body is
more efficient in how it uses its energy, so it makes it harder to lose weight.
There is individual variation in how much people fidget. It can result in the expenditure of
You can be more or less physically active. This is where you have the most discretion in terms of
increasing your energy expenditure. You can reduce your energy intake by eating less. You can
increase your energy expenditure by moving more.
Our body temperature increases after eating because we are expending energy.
The energy expended varies with the macronutrients. We are efficient at fat and carbs. We less
efficient at protein because we spend more energy to absorb protein.
We store a 24 hour supply of glucose. We store enough fat to stay alive (e.g., provides enough
calories, but not nutrients) for 57 days.
The protein and carbohydrates are mostly used to meet the needs of the organism. The fat usually
gets leftover and gets stored in the adipose tissue. If you are in extreme energy balance, you can
be converting carbohydrates into fat. Slide 34
The major contribution to adipose tissue comes from dietary fats. The minor contribution to
adipose tissue comes from carbohydrates and protein.
At the systemic level, this maintains the function of vital organs, fuels physical activity and the
absorption of food.
Hierarchy of nutrient use. Dietary fats are stored when there is a positive energy balance.
Body composition is divided up into two parts: lean tissue and fat tissue.
The older person has a higher body weight that is made up of fat.
Visceral fat is a rapid source of energy. This is fine if you are in negative energy balance.
This forces the pancreas to pump out more insulin because fat has to take up glucose.
You can be apple- or pear-shaped irrespective of gender. Men tend to carr