How do we utilise energy in a deficit?
Dear people that have the unfortunate belief that calories don’t dictate weight loss and calories in calories out doesn’t work.
I feel a little bit sorry for you for not being able to grasp reality.
For all you other intelligent beings here’s a little bit of info and logic.

Your body. That's right, all of you. You’re not that uniquely special. Have an average TDEE Total Daily Energy Expenditure. This is the average amount of energy you require each day. Your energy comes from food, and is measured in calories.
Calories are a measurement of energy in food.

Let’s say today your TDEE is 2500 calories. But you consume 3000 calories.
The extra 500 calories is surplus and will get stored as excess energy which is also body fat. Insulin is the hormone that will facilitate that, if it’s required.
Now what happens if you only consume 2000 calories? Well your body is still going to utilise 2500 if that's your TDEE, so it will take from your bodies stored energy, of which a lot is body fat. Therefore making up the 500 calorie shortfall.

If you continue to do this consistently over time. Consuming your calories in a shortfall. You’ll continue to utilise stored body fat to make up the difference, and as that gets used you’ll drop weight in the process.
Now people will bang on about we don’t absorb all the calories in food, people absorb at different rates, hormones affect how calories are used and or absorbed and stored etc.
Correct. But none of that negates the fact if we’re running short of energy we will utilise our stored energy and lose weight. Albeit these things can affect the efficiency of. Hormones, metabolic issues, medications etc cannot create mass from zero.

All of these points people raise are coming from an uneducated position. They’re all factors either side of the equation that is calories in calories out.
Because that's the summary description of a complicated equation.

Calories in food, absorption etc. Correct, there will be variations.
Nobody is saying 2500 calories is exactly 2500 calories absorbed. Or there’s exactly 2500 calories within the food. Food labels also do have variations within guidelines. But that's why we engage other approaches alongside to adapt and adjust as per the individual. Basing the approach on what we know.

-The calorie requirements.

-The calories stated in the foods.

-Track measurements.

Are we losing weight? Yes stay on track.
No, make adjustments whichever way measurements are indicating.
Carry on.
This will also make allowances for metabolic adaptations.
Whereas what was working was based on original start point. If you’re 10kg down now. You’ll have different calorie requirements.
Some of this may also explain why you see people claiming they’re in a calorie deficit and not losing weight.
They work out a calculation they believe is their calories but it’s not.
Albeit the issue here is mostly bad tracking, being completely unaware of consumption and not being honest with yourself.

So. Sorry to say it’s not some hack or special hormone balancing trick. It’s the basics. It’s always the basics and always has been. But like every industry, to sell more they have to recreate and package things differently. Just so you can blame your last approach and not yourself. Because trying to maintain A calorie deficit is hard and its easier to miss the wood for the trees.

But you know whats harder. Having to live with poor health and dissatisfaction.

As you can see Calories in and Calories Out albeit a simple summary is the result of a lot of interactions that grifters try and twist around to something its not. As shown by these images


Energy in a Deficit