Growing up, my mom regularly made healthy school lunches. I would choke down my whole-wheat wrap while enviously watching kids in the cafeteria feast on junk food. I was the fat kid, but the other kids never seemed to gain an ounce of fat sustaining on french fries, soda and candy.
I used to wonder what the hell was going on? Now I know, and if you’re trying to lose or gain weight, I think it’s helpful to understand why people gain weight.
So where did my fat come from? Why do people gain weight?
Food is a lot of things, but in the context of gaining weight, let’s think about food as a source of energy.
We are surrounded by a surplus of food – more food than our genes ever expected to process. For most of human history, we wandered around searching for our next meal. Our body still processes food with the expectation that we don’t know where our next meal is coming from.
The abundance of available food means an abundance of available energy. We also know – thanks to the laws of thermodynamics – that energy can not be created or destroyed within a system. Energy can only transfer or change. So how does all the extra energy in food change in our body? Why is some energy stored and some energy used immediately?
Food contains different amounts of three “energy” sources: Protein – which is a bunch of amino acids linked together – for building our muscles and immune system; Fat for concentrated energy that can take a while to use for a variety of functions; And carbohydrates – which is chains of “sugar” molecules in different lengths – for immediate energy that our body can quickly put to use.
The different amounts of each energy source can give our bodies clues about how to apply the energy in the food we eat.
When we take a bite of food, our body is inspecting the different types of energy in the food. Are we eating this fruit because want energy right now to run around? Are we eating these nuts for the fats to slowly give us energy in the cold winter? The ratio of the different energy types signals the body to engage different processes.
Keeping Energy For Our Engines
To understand the primary process for storing energy, imagine an old steam locomotive train.
Every day, the train staff loads up the train with coal for the engine. The train staff knows how far they will go every day, and they know how much coal they need to get that distance. The process your body uses to manage energy in food is like how the train staff manages coal for their train.
If the train needs to choochoo 100 miles in a day, and one bag of charcoal will power the engine for 10 miles, the train staff will need 10 bags of charcoal for the trip, and maybe, they take 11 bags – just to be safe – and store the extra bag in a little closet.
Well one day, the train goes by a coal mill giving away an endless supply of coal. They stop the train. They only have 5 more miles to go for the day, but they will have 10 miles to go tomorrow. The train staff loads up 5 bags for the rest of the day, and since the mill is giving away the coal, they decide to load up coal for tomorrow too.
They recruit more staff for the train. They work together boxing up extra bags of coal to put in the spare closet.
The closet fills up pretty quickly, but there is still free coal at the mill. They’ll probably go another 10 miles every day for the next month. They can’t just leave behind free coal. They start putting the boxes of coal into cartons and filling all the wagons behind the engine with cartons of coal.
Before they know it, all the wagons are full of coal, and the train departs from the coal mill a lot heavier than when it arrived.
Poor Eating Can Fill Our Wagons
This train story is like a person eating lunch at an all-you-can-eat buffet.
When you grab the first tray of food, your body starts breaking down the carbohydrates in that food into glucose – the most simple “sugar” molecule.
Glucose is energy for every cell in your body. This creates immediate energy for everything that makes us function. When our body recognizes glucose floating through our bloodstream, our pancreas releases a hormone called insulin. Insulin let’s glucose enter cells in our body to become energy. Insulin is the key that unlocks the door on a cell’s surface to let the glucose come in and power up the cell.
Insulin is the train staff bringing bags of coal on to the train.
When you grab the second tray of food, insulin starts to realize you have enough glucose now for the rest of the day, so the extra glucose should be stored somewhere in case you need it later. The pancreas produces more insulin.
The additional insulin starts working on glycogenesis – which is turning glucose into glycogen to be stored in the liver. The same way the train staff recruited more staff and filled the closet with extra bags of coal, insulin boxes up glucose as glycogen and stores it in the liver – and some directly in muscles too. Glycogen is easy to convert back to glucose when the body needs energy.
Unfortunately, the liver can’t hold a lot of glycogen – only about 100 grams, which is about 400 calories worth of glucose.
When you finish your second tray of food and grab a tray from the dessert bar, insulin starts to realize that the liver is completely full of glycogen, but there is an opportunity to store more energy for a future day. The pancreas produces even more insulin.
The insulin starts working on de novo lipogenesis – which is creating fat from the glucose to eventually be used or energy. The same way the train staff started putting cartons of coal in all the wagons on the train. The staffed wanted to make sure it had energy if it ever needed it. The insulin stores the glucose as fat to make sure there is energy if the body ever needs it.
Every time you eat more energy than you need at the buffet, your body adds wagons to the train to store more fat.
How Do You Keep Your Wagons Empty?
If you reduce the body’s need to produce insulin, your body can’t store as much energy as fat, so think about what foods will add glucose to your bloodstream because higher glucose levels signal the pancreas to produce more insulin. For example, pure sugar spikes your blood with glucose and triggers your pancreas to crank out insulin for storing all that glucose.
Lifestyle can also play role. One big example is stress. Stress adds glucose to the bloodstream – which makes sense if you think about it. Stress produces the hormone cortisol to engage our flight or fight response, you need glucose in your blood to have the energy to either run or fight.
There are interesting ways to manage your glycemic load and insulin response. Legumes and lentils offer a cool benefit known as the “Second-Meal Effect.” Not only do legumes and lentils protect our glycemic load and insulin response while we are eating them, but they also lower our glycemic response the next time we eat – even if the next time is hours later.
Most people think getting fat is from overeating – which definitely can cause weight gain because of the amount of insulin triggered by overconsumption, but overeating is not the only way to gain weight. What you eat, when you eat it and your hormone levels – which are commonly influenced by stress, sleep and exercise – are huge factors.
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