Today I am going to talk about the science behind health! How does your body functions? What is the role of various nutrients?
Like any moving vehicle, your body needs fuel to function. The best part is your body uses multiple fuels. The body uses these fuel to generate energy which is transported to different parts. The process by which body converts this fuel into energy is called metabolism. Does food directly acts as energy for the body? Food contains ingredients that acts as fuel. However these ingredients are not a direct source of energy that can be used immediately.
Food contains the following ingredients that are used to generate energy & transport to different parts of the body:
Protein
Fats
Carbohydrates (includes sugar)
Fibre
1 gram of protein & carbohydrate contains 4 calories(kilocalories) each while fat offers 9 calories per gram. Fibre contains 2 Kcal per gram & helps in making digested food leave your body.
So what are these sources of fuel that are converted into energy? Your body extracts at 3 of the following fuels from what you consume
Free fatty acids
Glucose
Amino Acids
Fats converted into fatty acids
Fiber
Carbohydrates converted into glucose
Protein converted into Amino acids
Now it is important to understand how these fuels are stored in the body. Different fuels are stored in the body in different forms, different amounts & at different locations.
Fatty Acids: Any cell can store fatty acids. They can also be transported directly into the bloodstream. Body does not have enough cells to store fatty acids but can generate special fat cells which put together are called “adipose tissue’. The body can store tens of kilos of fat. Each kilo of fat is sufficient to give energy to individual for many days. An average built person contains sufficient fat that gives enough energy to survive for a month. You can survive without carbs. Without essential fats your brain can stop working. So you should never cut down fat consumption. Your body needs essential fats everyday for survival.
Glucose: Glucose is a small molecule & can easily travel from cell to cell. This is not suited for storing sugar & therefore for storage sugar is converted into glycogen. Glycogen is a molecule which consists of smaller glucose. This size makes it easier to store glucose. As glycogen, sugar is stored in liver & muscles. Both these body parts can convert glucose into glycogen. Liver can convert glycogen back to glucose but muscles cannot. Muscles can use glycogen directly or release it into the bloodstream. It is important to note that only a small amount of sugar can be stored. Ingested glucose & table sugar directly travel into the bloodstream. This means that the amount of glucose allowable in the body can easily exceed than required. People with average weight will have 5 grams of sugar in their blood at any given time. Any level beyond 10 grams is considered high. When glucose enters our body in excess of 10 grams through the food we eat, our body releases insulin which instructs liver & muscles to absorb the glucose from blood. Therefore all parts of the body which run on glucose start functioning really well. Hence burning of fatty acids for energy production is reduced. Glucose storage can easily be depleted in one day, making it a short term fuel. Complex carbohydrate cannot be directly transported to bloodstream & needs to be converted first, which takes time. This is good for the body since it ensures that bloodstream will not be flooded with glucose & body will not be required to release extra insulin.
Protein & Amino Acids: These are found throughout your body either bunched up as protein or freely flowing as amino acids. They can be used to form muscle fibre or cells which can again broken down into protein & amino acids. Proteins are broken down into amino acids in intestine & then brought to liver which is then partly assembled & partly released into blood stream. Compared to glucose, protein or amino acids is available for use at any one time. Amino acids have huge uses. They make up your DNA
Actual energy
Now you have all the fuel stored but you need that trigger to convert it into energy. This energy is called Adenosine Triphosphate (ATP). As shared earlier, body stores fuel in 3 different sources. To be used as energy, each of these fuels should be converted into ATP.
Glucose: Glucose stored in the form of Glycogen can be converted into ATP by all cells containing mitochondria. All cells have this power producing unit which means that all cells can convert glucose into ATP. Muscles can burn Glycogen directly without need to convert into glucose.
Fatty acids: Same goes for fatty acids with the exception of brain. However the brain uses a lot of energy in the form of glucose. Fatty acids can be converted into Ketone which can partly power brains. However brain still needs glucose which comes from protein & if you do not consume enough protein it comes from breaking down the muscles
Amino Acids: Liver can convert amino acids into glucose or into fatty acids
The following discussion is important
Almost everything can be converted into everything else in the body
Glucose to Glycogen to Stored fat: This happens when your sugar intake exceeds storage capacity.
From storage fat to glucose: This is called gluconeogenesis & gives energy to the brain using fat
How the energy is used by the body?
Energy is used when you indulge in physical activity however the majority of work happens without you noticing it. This energy expenditure is measured by Basal Metabolic Rate. For instance, the body uses energy for pumping blood to different parts. Energy is used by the brain, to keep your body warm. Our active functions requires less energy as compared to BMR. However indulging in exercise increases your BMR. The body does not always spend energy in same amounts & in same way. Body can continue to go on with the available fuel. It burns a lot of energy when available in abundance & uses less in its absence. It also means asking for more energy even when lot is available.
Adults carry enough energy to survive for a month. Still if you skip lunch you will feel hungry even before dinner time. This happens because the body is attached to its energy stores. We eat more than our calorie requirement & grow overweight but still you will feel hungry even if you miss a single meal.
Whenever body runs short of fuel, it sends a signal that you should eat although body can easily switch to the fuel source to generate energy. So if fuel has reached body for a while, the body starts conserving energy. This can be done in a lot of ways, lowering body temperature, slowing down brain etc.
Conclusion
In order to lose weight, please consider the following:
Energy has to be used & not stored in the body.
Energy use should not be diminished. Instead it should be increased through efforts.
Stored fuel should be able to give the energy body requires.
More energy must be spent that is added. If you eat less, you will actually gain weight in the long run.
