Fatty acid synthesis is how our bodies make fat, and it changes depending on what we eat and how much energy we need. When we eat foods, especially those high in carbohydrates, our body adjusts how it processes fat to keep our energy in balance and store any extra energy.

How Nutrition Affects Fatty Acid Synthesis

1. Fed State (When We've Eaten):

   • After eating, especially a meal with lots of carbohydrates, insulin levels go up. Insulin helps our body take in glucose and also encourages the making of fat, called lipogenesis.
   • The enzyme Acetyl-CoA Carboxylase (ACC) gets turned on. It changes acetyl-CoA into malonyl-CoA. This is an important step in making fatty acids.
   • Substances like citrate (which increases when we have more energy) are moved from the mitochondria (the powerhouse of the cell) to where fatty acids are made.

2. Fasted State (When We're Not Eating):

   • When we haven't eaten for a while, levels of a hormone called glucagon go up and insulin goes down. This stops ACC from working.
   • Instead of making fat, our body focuses on breaking it down. Hormones like epinephrine help to break apart stored fats, which releases fatty acids into the bloodstream.

Important Ways Fatty Acid Synthesis is Controlled

• Hormonal Control:

  • Insulin is a key hormone that helps make fat. It encourages fatty acid synthesis but slows down fat breakdown.
  • On the other hand, glucagon and epinephrine help the body break down fat when we need energy.

• Food Availability:

  • Eating a lot of carbohydrates increases insulin, which helps create fat. If we eat fewer carbohydrates or a higher-fat diet, fat creation slows down, and breaking down fat becomes more common.

• Other Regulation:

  • Citrate helps activate ACC, boosting the fat-making process. Meanwhile, long-chain fatty acids can slow down ACC, signaling that there is already enough fat available and that the body should stop making more.

Example: How Our Diet Affects Fat Making

Let's say we eat a meal high in carbohydrates. After eating, insulin levels rise, which leads to:

• More glucose entering cells
• Extra glucose being turned into fatty acids

On the flip side, if we go a long time without eating or follow a ketogenic diet (which is low in carbs), the hormones change, leading to:

• Less activity of ACC
• More breakdown of fatty acids for energy or production of ketone bodies as an alternative energy source.

In Summary

Learning how fatty acid synthesis works helps us understand our health better. The balance between making fat and breaking it down depends on what we eat. This balance affects how our bodies store and use energy. Properly managing this process helps us keep our energy levels steady, adjusting to what our bodies need at different times.