PTC: Module 4 - Carbohydrates

The Glycemic Index (GI) is a ranking of carbohydrates on a scale from 0 to 100 based on how much they raise blood sugar levels after eating. Different carb sources can affect the rate at which glucose appears in the blood.

No, diets with different sugar levels but the same number of calories result in the same body composition. Simple and complex carbs are equally fattening.

Complex carbohydrates have three or more sugars and include oligosaccharides and polysaccharides.

Lactose intolerance is the inability to digest lactose due to low lactase activity, leading to discomfort, bloating, and abdominal distension. It is particularly prevalent in African Americans, Jews, Arabs, Greeks, and some Asians.

No, numerous studies have shown that low-GI diets are no better than high-GI diets for reducing body weight or body fat.

Fiber improves digestion, glucose control, and immune system function. It also lowers the risk of cardiovascular diseases, aids fat loss, and increases gut microbiota diversity.

The daily fiber intake recommendations are 38g for men and 25g for women.

Simple carbohydrates include monosaccharides and disaccharides such as glucose, fructose, lactose, maltose, and sucrose.

By the time carbohydrates are fully digested, they are broken down into monosaccharides glucose, fructose, and galactose.

Carbohydrate tolerance refers to how well an individual can handle carbohydrate intake without adverse effects. It varies based on factors like insulin sensitivity, body composition, and genetic predisposition.

Polysaccharides include starch, glycogen, and cellulose. Starch is found in cereal grains, potatoes, legumes, and other vegetables.

High fructose consumption can lead to de novo lipogenesis, resulting in triglyceride accumulation in the liver, insulin resistance, chronic inflammation, and increased risk of cardiovascular disease.

Insulin helps lower blood glucose levels by inhibiting gluconeogenesis in the liver and facilitating glucose uptake by cells.

Strength trainees should consume some carbs before and after workouts, but overall carb intake is less critical than protein intake for muscle growth and performance.

Glycogen stored in muscles and the liver is broken down into glucose to provide energy during exercise, especially during high-intensity activities.

Oligosaccharides are found in beans, peas, bran, and whole grains. They cause flatulence because digestive enzymes cannot hydrolyze all kinds of oligosaccharides, leaving bacteria in the intestines to digest them.

Fructose is primarily metabolized in the liver, where it can be converted to glucose, stored as liver glycogen, or broken down into pyruvate for energy. It can also be converted to fatty acids.

glucose; fructose

1. Diarrhea

2. Bloating

3. Stomach cramps

Fructose toxicity is only a concern for people who consume large amounts of processed foods with added fructose.

Insulin cannot store what isn’t there - energy balance still applies. If insulin made someone fat, anyone on a high-protein diet would become fat as protein is insulinogenic. At the end of the day, when it comes to fat loss, a carb is a carb.

1. First off, you would need to be in an energy surplus.

2. The body preferentially stores fat as fat and burns carbs for energy; however, any carbs you eat and burn as energy frees up more fat that you consumed to be stored as fat.

3. When your body’s fat storage rate exceeds what it can use from your dietary fat intake, it can convert the carbs you intake to fat via de novo lipogenesis.

4. Overfeeding on carbs will cause increased glycogen storage after which extra de novo lipogenesis occurs to store the remaining carbohydrate excess.

1. There is insulin resistance with high insulin production but not too high blood glucose levels.

2. Later, insulin production becomes exhausted and blood glucose levels rise as a result.

oxidative stress

blood glucose
nutrient partitioning
chronic inflammation

TEF
energy expenditure

appetite suppressing
hunger levels

Carbohydrates stimulate both serotonin and dopamine production. While these neurotransmitters are normally well-regulated by the body, if an individual has abnormal levels of either, carbohydrates can significantly impact their physical and mental performance and their motivation.

1. High BF%

2. Genetic ancestry is close to Africa or India

3. Men and women with PCOS (normally women are unlikely to become carb intolerant due to superior insulin and glucose metabolism)

4. Older individuals

5. Sedentary individuals

Bloodwork. Do a panel for type-II diabetes and the test should consist of:
1. An oral glucose tolerance test that measures fasting blood glucose and postprandial glucose after a high-carb meal;
2. Fasting insulin concentration; and
3. A glycated hemoglobin (A1C) test - a measure of average blood glucose levels over the past few months

TCA (Krebs) cycle

1. Creatine phosphate system (phosphocreatine system, ATP-CP)

2. Glycolytic system (anaerobic glycolysis, lactate system)

3. Aerobic system (aerobic glycolysis, TCA cycle)

The aerobic system depends on oxygen, therefore it is limited by VO2 max (the point at which further increase in exercise intensity can no longer produce an increase in the volume of oxygen uptake).

85

50

85; carbohydrate

10-25 seconds; 3 minutes

ATP is produced by the incomplete, anaerobic breakdown of glucose through phosphorylation into lactate.

Skeletal muscle: 350-500 g
Liver: 80-120 g

Muscles can only use their locally stored glycogen as fuel. The liver can breakdown its glycogen into glucose where it re-enters the bloodstream to be absorbed and used by the skeletal muscles that need it.

The liver can both produce glucose (via breaking down its glycogen stores) and reduce blood glucose levels when these levels become too high.

1. Performing over 10 sets per muscle group in a single workout.

2. Training twice on the same day with high volumes.

It can be posited that generally you only need ~80 g of carbs to fuel a typical strength training workout. This assumes:
- 500 kcal expended
- 16% of energy is produced by the ATP-CP system (lower end of range based on research)
- 20% of energy is produced by the aerobic system (lower end of range based on research)

Since your skeletal muscles store between 350-500 g, you would not exhaust your glycogen stores from the workout. You can also expect to achieve full glycogen resynthesis before your next workout (even if it is the following day).

1. Amino acids - all amino acids except lysine and leucine are gluconeogenic and therefore can be converted into glucose.

2. Fats - the glycerol backbone from triglycerides can be converted into glucose by the liver; therefore if someone is on a low-carb, high-fat diet (e.g., keto) then there should be an adequate supply of TAGs to make a major conversion of glycerol to glucose plausible.

3. Lactate - the Cori cycle recycles lactate produced during anaerobic exercise into glucose.

insulin and glucose

No. Carbohydrates do not contribute to or improve MPS but they do suppress MPB due to triggering an insulin release. However, protein is also insulinogenic and it also stimulates MPS. Therefore, it is redundant to consume carbohydrates post-workout if you are already consuming enough high quality protein (at least 0.4 g/kg).

The fiber binds to water and certain nutrients which turns the fiber into a thick, viscous gel which delays gastric emptying and food transit times.

1. Reduced LDL levels

2. Reduced blood pressure

3. Improved blood sugar levels

4. Improved insulin sensitivity

Dietary soluble fiber generally contains 2 kcal per gram (and sometimes even less or negative calories) due to their anti-nutritive effects. An increase in dietary fiber intake can decrease energy balance by a few percent due to fecal energy losses (literally “pooping out energy”).