Hydration is key for fat loss!!!
This is a comment we have all heard before, no one disputes this, but does everyone really understand how or why, or the level of importance it holds?
A simple metabolic assessment that measures the O2 and CO2 in your breath and shows some very interesting changes from a single glass of water.
The tests in the image was repeated several times for fidelity and show a stark contrast between hydrated and dehydrated metabolism.
This test was performed on a 30-year-old male in a rested but dehydrated state, previous tests showed a 90%+ use of fats as fuel and low-stress markers. The first test in a dehydrated state showed fat use of 17% with a 1,000 kcal increase in energy expenditure on average of a 10-minute analysis. After a single glass of water, the % of fuel used as fat at rest went from less than 17% to just over 63% and kcal back down to normal range.
This can be explained by two aspects of normal function, 1 the first stage of beta-oxidation or the burning of fats as fuel is hydrolysis, the use of water to break the carbon bonds, no water, no beta-oxidation. Second dehydration will be a physiological stress likely to increase sympathetic dominance, with an individual that has the resources to mount a stress response this sympathetic spike will increase the use of energy as a natural reaction to stress. This response will resolve if continued for over 3 months and drop back down to normal levels as seen in many studies on stress response. Although, once this response has been exhausted in this way, the capacity to mount a stress response in the future will be changed as will related pathways.
There are many considerations when looking at the use of fat as fuel, not just hydration, let’s start by looking at the journey of a molecule of fat, once eaten. First, its shape and form will be altered by your teeth and stomach acid like all foods, it then is emulsified in the small intestine before being absorbed. Depending on its size it may either enter the lymphatic system as something called a chylomicron or, if small enough, straight into the portal vein like most food heading straight to the liver. Chylomicrons un the other hand will be dumped into the blood at around the thoracic duct, these fats are either stored or used as fuel in beta-oxidation but as they travel have the potential to be oxidised by excess free radical production which is where specific anti-oxidants like vitamin E protect fats and cholesterols. During beta-oxidation fats are broken down into a number of steps but before that, it must be transported inside the mitochondria. This is achieved with the help of specific proteins like L-carnitine to shuttle the fat across the membrane of the mitochondria. Once inside the fatty acid is broken down in order to produce acetyl CoA, FADH2 and NADH for the Krebs cycle and electron chain transport to allow energy production. The first step in this process is hydration, so when we are dehydrated for example it is easy to see why beta-oxidation falls considerably. The next steps involve co-factors such as FADH2 and NADH which vitamins like B2 & B3 are vital for.
The liver is also an important player in the metabolism of fats as it not only processes them but also produces bile from various products including cholesterol. The liver is a major regulator of cholesterol, not dietary intake (which has zero effect of circulating cholesterol) despite what some might say. Bile is massively important in the emulsification of fats during digestion and vital to their proper absorption, vitamin C actually plays a huge role in assisting the addition of cholesterol to bile as well as the level of beta-oxidation that occurs within brown adipose tissue during cold thermogenesis (burning of fat to produce heat).
We can see that fat burning does not simply just happen because you have consumed less calories then what you need to function, although that is a player if it is the only aspect then calories are much more likely to come from other tissues.
This is not exhaustive I have not touched on subjects like amino acid metabolism that affects or is affected by beta-oxidation and changes in resources or epigenetic signals created in the environment but it is clear if we want proper fat loss and not just weight loss it is important to consider overall resources such as micronutrient and hydration status as well as total calorific consumption.