Weight Loss and Exercise

Okay, I'm starting to lose my ability to take this unit seriously due to the simplicity of the content, but here goes anyway.

Dieting

1. Be able to explain the difference between fasting and starvation
2. Be able to explain the key changes in metabolic pathways during fasting and starvation

Fasting is basically what happens when you stop eating for a short time. When you are fasting, fatty acids from adipose tissue are exported to the plasma and glycogen is broken down to maintain blood glucose.

When glycogen stores are depleted (takes ~2 days), you enter a starvation state. During this time, your body basically converts everything else into energy. Amino acids are broken down: carbon skeletons of glucogenic amino acids are converted to glucose, whereas the amino groups are converted to urea. Fatty acids are oxidised to ketone bodies, which, if allowed to accumulate, can cause ketosis. Ketosis decreases appetite and causes nausea, and ketones can be smelled on the breath. (See here for more details on ketoacidosis.)

3. Be able to discuss the different types of diets.

This lecture covered four types of diets:

1. Low carb, low fat, high protein (e.g. Total Wellbeing Diet): Basically what it says on the box. Weight loss is initially rapid, and will continue so long as calories in < calories out (the most important part of any weight loss diet, as I'll reiterate soon). The high protein may help with satiety (feeling of fullness), which is probably why these diets are so popular. After all, if you feel full more quickly, you'll probably eat less.
2. Low carb, high fat (e.g. Atkins Diet): The key principle behind this is the development of ketones. I'm not sure why this is desirable, given what I just said about ketosis, and sure enough some of the common consequences of this diet include dehydration, weakness, headaches and dizziness. Furthermore, adherents to this diet may have inadequate amounts of fruit and vegetables.
3. Fad diets: These come in all shapes and forms, but most are pretty extreme. One example of a more extreme diet that comes to mind is the 30 Bananas a Day diet. Fad diets are generally not backed up by scientific evidence. They might help lose weight, however, if calories in < calories out.
4. Portion control: This is literally just calories in < calories out without getting too caught up in the details.

4. Understand the purpose of dieting in the context of fuel mobilisation and losing weight

Dieting, as I hope you've figured out by now, is simply trying to make sure you consume fewer calories than you expend. I've also touched on that here.

5. In the context of losing weight, understand the role of macronutrient proportion and macronutrient intake.

In the context of losing weight, macronutrient proportion isn't that important. As long as total calories in < total calories out, you will lose weight. Of course, adequate intake of macronutrients are important for other reasons (protein for building muscle, fats for absorbing fat-soluble vitamins, etc.), just not from a weight loss perspective. Hence, if you want to lose weight by going on a diet, anything that you will stick with is fine, as long as calories in < calories out.

Physical Activity

1. Be able to discuss the benefits of physical activity

Physical activity has plenty of benefits, including reducing "all-cause mortality," which I'm assuming is a misnomer, or else exercising would prevent us from dying in car crashes and so forth. (Don't get me wrong- it would be great if exercise could do that, but I'm not going to hold my breath.) It also reduces the rate of high blood pressure, some cancers, type 2 diabetes and so forth. Aside from preventing you from dying, it also improves your bone health, cognitive function, muscular fitness and so on.

2. Be aware of the guidelines for physical activity for Australians

It's recommended that you get at least 150min/wk of moderate physical activity. If you are exercising more vigorously, 75min might do the trick.

3. Be able to describe aerobic activity and its components

Aerobic activity is what is sometimes more colloquially known as "cardio": running, cycling, dancing, swimming, etc. It can be studied in terms of different components, such as intensity, frequency and duration.

4. Be able to describe muscle-strengthening activity and its components

Muscle-strengthening activity involves resistance training, lifting weights and so on. The components of muscle-strengthening activity are intensity, frequency and repetitions.