“We cannot wait for society to catch up to science to make decisions that determine life or death.”
Quoted from the Netflix TV series, the phrase “you are what you eat” sparked a deep reflection on the complex relationship between diet and overall health. While countless evidence-based, science-backed studies exist, the truth often gets muddled in today’s social media-driven environment. It can be challenging to filter out the facts from the noise, especially when health organizations and influencers might not always share the whole story. This blog explores the essential components of a balanced diet, the metabolism of key nutrients, and how understanding these processes can help optimize your health and fitness journey.
Table of Contents
Components of A Diet
- A balanced diet is not just about eating in moderation; it includes the right combination of macronutrients (carbohydrates, proteins, and fats) and micronutrients (vitamins and minerals) along with water, which is crucial for all bodily functions.
- Carbohydrates are primarily derived from whole grains.
- Proteins can be sourced from legumes, nuts, and lean meats.
- Fats come from healthy sources like vegetable oils, nuts, and seeds.
- Understanding how these nutrients are metabolized helps us make informed choices that align with our health and fitness goals.
Sources? Check.
Amount / Recommended Daily Intake? Check.
How are these components metabolized in our body? Let’s find out below.
Carbohydrate metabolism
Carbohydrates are available in our body in the following forms: liver glycogen, muscle glycogen and glucose in the bloodstream, with liver glycogen being the primary storage form.
Liver glycogen maintains blood glucose levels, which can be depleted during muscle utilization of ATP.
Carbohydrates can undergo both aerobic and anaerobic oxidation.
What is aerobic and anaerobic oxidation?
- It’s essentially using the same source i.e. glucose either in the presence of oxygen or the absence of oxygen. The type of oxidation taking place depends on exercise intensity and muscle fiber activation.
- Aerobic oxidation generates energy amounting to 30 ATP (Adenosine Triphosphate, the basic unit of energy) as opposed to anaerobic oxidation which generates 2 ATP units per glucose molecule.
Fat metabolism
Free fatty acids are the immediate fuel source for muscle cells. Fats are stored as triglycerides (chain of three free fatty acids) majorly in adipose cells as well as skeletal muscles.
Fat metabolism and breakdown can only take place in mitochondria through a process called beta-oxidation.
What is the crossover concept and how do we apply it during training?
The fatty acid sources mentioned above are the major sources of fuel during exercise intensities between 45 to 60% of VO2 max. This is because,
- During low exercise intensities, slow, oxidative muscle fibers i.e. type 1 muscle fibers are activated. These fibers are more resistant to fatigue and promote greater fat utilization
- During higher exercise intensities i.e. 80% VO2 max and beyond, type 2 muscle fibers are recruited. There is a switch in energy sources from free fatty acids to glucose (present in muscle stores and blood. This is the crossover point and is mentioned in the graph below.
As a person gets deep into the exercise session, liver glycogen, blood glucose levels, and intramuscular triglycerides begin to deplete and now, the body has to tap into the fat reserves from the adipose tissues.
The preferred fuel for muscles crosses from carbohydrates to fats. Therefore, a submaximal steady-state exercise program works best for fat burn.
The rationale behind the crossover concept.
To understand why there exists a switch in the fuel source from carbohydrates to fats during prolonged exercise intensities, we need to understand the concept of endurance.
Endurance refers to the ability to perform repetitive or sustained activities over a prolonged period.
- Cardiopulmonary endurance refers to dynamic motor activities like cycling and swimming (involving large muscle groups of the body).
- Muscle endurance also called local endurance is the ability of the muscle to contract repeatedly against resistance over a prolonged period.
When a person starts an endurance training program, the following key changes occur
- There is approximately a 2-fold increase in mitochondrial content after months of regular training. Now we know that fats can only be used as an energy source in mitochondria, a greater mitochondrial content leads to greater fat consumption and hence, carbohydrate sparing.
- Since the carbohydrates are being broken down aerobically, a greater amount of energy is produced for the same glucose molecule. This, coupled with greater mitochondrial content, leads to carbohydrate sparing.
Due to the following reasons, there is a greater fat utilization at low-intensity, prolonged exercise regimes (endurance regimes).
Protein metabolism
We all know how protein is required to build muscles. Certain amino acids directly contribute to ATP production.
- The ideal normal protein intake is 0.8g protein/ kg body weight.
- For high-intensity endurance training, 1.2-1.4 g/kg/day.
- For strength training, 1.2-1.7 g/kg/day.
During the initial period (first few days) of training, the body breaks down proteins (negative nitrogen balance), hence it is important to optimize protein consumption especially when starting with a new regime.
Fun fact: Do you ever wonder why trainers/doctors tell you to consume protein post-workout?
Well, muscle protein synthesis decreases during exercise since the ATP-utilizing process of protein synthesis is inhibited to preserve ATP for mechanical work. Similarly, protein synthesis increases during the recovery period which makes post-workout the best time to have those protein meals.
Effects of endurance and strength training
| STRENGTH TRAINING | ENDURANCE TRAINING |
| – Increased muscle protein | Increased mitochondrial protein synthesis |
| – Increased Cross Sectional Area | Increased mitochondrial number and size |
| – Increased Strength | Enhanced aerobic ATP resynthesis |
Conclusion
There exist different forms of training. A good plan is said to be one that consists of aerobic training, resistance training and mobility work. A basic overview of how different nutrients get metabolized in the body, will help us make better food choices, and train in a more goal efficient manner.
There exists a gap between training and nutrition, and it is of utmost importance to know how our body reacts to the foods we consume and how it get’s utilized in our body. Once we know the science behind exercise and nutrition, making healthy choices won’t be as confusing as before.
