Lecture #26 Flashcards
Describe how glucose demonstrates versatility in the human body.
Glucose is versatile as it can be used to generate energy through both anaerobic (without oxygen) and aerobic (with oxygen) pathways. This allows for energy production to transition from low to high intensity exercise effectively.
Why is glucose essential for erythrocytes and the renal medulla?
Glucose is crucial for erythrocytes (red blood cells) and the renal medulla because these tissues rely on glucose for energy, as they either lack mitochondria or are in low oxygen environments, making glucose an essential energy source.
Describe the body’s capacity to store glycogen and its significance for physical activity.
The body stores glycogen in a 1:3 to 1:4 ratio with water, primarily in skeletal muscles and the liver
enough to support 1.5 to 2 hours of exercise. This explains why marathon runners may experience fatigue after the 30km mark, often due to muscle glycogen depletion.
What does the statement “Fat burns in the flame of carbohydrate” mean?
This statement suggests that carbohydrates are necessary for fat metabolism. It underscores the idea that fat is metabolized more efficiently in the presence of carbohydrates, a concept that has sparked controversy and debate.
What is carbohydrate loading and its purpose?
eat as many carbs as possible prior to race so you can fuel up muscle and liver glycogen stores (start race with maximum glycogen stored)
What was Dr. William Harvey’s stance on carbohydrates
Dr. William Harvey recommended a diet forbidding sugar in all its forms to address corpulence and related diseases, emphasizing the elimination of sugar at every meal.
Describe the key principles of Dr. Atkins’ low carbohydrate diet
Dr. Atkins’ diet limits carbohydrate intake to less than 20 net grams per day to induce ketosis, requiring subjects to drink 8 glasses of water daily.
It controversially claimed that one could lose weight on a high fat and protein diet with low carbohydrates, even without exercise.
What was the American Medical Association’s stance on low carb diets
The American Medical Association criticized low carb diets, stating they had no novelty or scientific merit. It raised concerns over the unlimited intake of saturated fats and cholesterol-rich foods, and doubted their basis for long-term healthy weight reduction or maintenance.
What is the rationale behind maintaining low insulin levels in a low carbohydrate diet?
A low carbohydrate diet aims to maintain low insulin levels to prevent lipogenesis (fat storage) and promote the breakdown of fat, since insulin is the main hormone that drives the accumulation of fat in adipose tissue.
How are carbohydrates reintroduced in a low carb diet and what is the effect?
Look at graph on DOCS for study info
Carbohydrates are progressively reintroduced in the diet after initial restriction. This gradual incorporation often leads to difficulty in maintaining carb restriction and can result in weight gain, diminishing long-term effectiveness.
What were the long-term effects on body weight in a 2-year follow-up of low carb vs. low fat diets?
Initially, weight loss was about 3 times higher in low carb versus low fat diets. However, this was not maintained; after 2 years, weight loss was nearly completely reversed, indicating that the effectiveness of low carb diets decreases over time.
What explains the initial higher rate of weight loss with low-carb diets?
Initial weight loss in low carb diets is higher due to:
- the loss of glycogen-bound water
- the production and elimination of ketones (a byproduct of fat metabolism)
- increased energy expenditure from metabolizing fat
- increased satiety leading to reduced food intake.
How does the loss of glycogen affect weight on a low-carb diet?
When glycogen stores are depleted, the associated water stores are also eliminated, contributing to a rapid decrease in water weight, which is often mistaken for significant fat loss.
What role do ketones play in weight loss in low-carb diets?
Ketones are byproducts of fat metabolism that are eliminated through breath and urination, representing an additional way of eliminating calories without consuming more energy.
What changes in energy expenditure occur with low-carb diets?
Low-carb diets can increase energy expenditure as the body processes fat and adapts to new metabolic processes, leading to greater initial weight loss.
How do low-carb diets affect satiety and food intake?
Low-carb diets increase satiety due to higher protein and fat consumption compared to carbs, resulting in reduced food intake as protein and fat are more filling and lead to lower variations in insulin levels, affecting hunger and satiety fluctuations.
What unexpected improvements in cardiovascular risk factors were observed in people on low-carb diets?
Contrary to initial expectations, people on low-carb diets saw greater improvements in some cardiovascular risk factors, with significant reductions in triglyceride (TG) concentrations, improved HDL-cholesterol levels (“good cholesterol”), and better indices of fasting insulin sensitivity.
How do improvements in blood lipids and blood pressure compare between low-carb and low-fat diets?
Improvements in other blood lipids and blood pressure were the same for individuals on low-carb diets and those on low-fat diets.
What are the most common complaints associated with low-carb diets?
The most frequent complaints from those following low-carb diets are constipation and headache, which can be attributed to lower intake of fiber due to reduced consumption of fruits, vegetables, and whole grains.
What is the ‘keto flu’ in the context of low-carb diets?
‘Keto flu’ refers to a group of symptoms, including headache, that mimic the flu and occur as the body adjusts to reduced carbohydrate intake and enters a state of ketosis.
What are some less common symptoms experienced by individuals on low-carb diets?
Individuals on low-carb diets may report halitosis (changes in the smell of breath), muscle cramps, diarrhea, general weakness, and rashes more often than those on low-fat diets.
How does the body adjust to a low-carb diet over time?
As time goes by, the body adjusts to the low-carb diet, potentially leading to a decrease in the initial negative side effects such as ‘keto flu’, constipation, and headaches.
