Want to lose weight? Here’s what you need to know in under 1000 words

One, you don’t want to lose weight: you want to lose fat. You don’t want to lose muscle or bone because they are very important functionally and metabolically. What you want to lose is fat. So weight loss needs to be reworded as fat loss.

Two, roughly speaking, the body is generally either storing surpluses or using reserves.

Three, the major fuels for the body are glucose and fatty acids.

Four, for the body to use fat reserves, insulin levels must be low. Fat cannot be efficiently utilized as long as insulin is high, because insulin promotes storage.

Five, the thyroid gland regulates metabolism and brain function. It requires adequate amounts of iodine without which it cannot work properly. To ensure healthy metabolic function, iodine supplementation is critical.

That’s what you need to know. If you want more details, I can expand a bit.

Insulin regulates fat storage

Every second that we are alive, trillions of biochemical reactions take place. The energy currency is adenosine triphosphate, ATP. Mitochondria produce ATP primarily using glucose or fatty acids. Fatty acids produces a lot more, but glucose is much easier to use. Both are used but one always dominates. In general, if there is glucose to be used, fatty acids are not much. For fat loss, we want to promote fat burning for ATP production to fuel cellular activity.

High glucose levels from carbohydrate intake trigger insulin secretion. This is necessary to bring the glucose into the cell, and to get rid of it from the bloodstream where it causes damage to the tissues by glycation. Within the cell, glucose can be either fermented without oxygen or oxidised with oxygen. Lower oxygen levels (and very high short term metabolic needs) promote fermentation. Higher oxygen levels (and lower metabolic ATP production rates) favour oxidation. More fermentation leads to greater accumulation of lactic acid, which further decreases oxygen levels. Red blood cells do not have mitochondria and therefore can only produce ATP by fermenting glucose.

Lower glucose leads to lower insulin. This triggers the release of fatty acids and glycogen into the bloodstream. If sustained, low glucose leads to the production in the liver of ketones primarily to fuel the brain whose cells can either use glucose, ketones, or medium chain fatty acids because longer molecules cannot pass the blood-brain barrier.

The higher the glucose, the higher the insulin, and the faster the uptake and storage of nutrients from the bloodstream into cells. The lower the glucose, the lower the insulin, and the faster the stored fat can be released and used.


Amount of glucose stored as fat and amount of fat released from fat cells as a function of insulin concentration. Plot taken from https://optimisingnutrition.com

The most metabolically active tissue is muscle. The more muscle we have, the more energy is used, and the faster both glucose and fat are burned to supply fuel to the cells. The more we use our muscles, and the more intensely we use them, the more they grow, and the more efficiently they burn both glucose and fat. Also, the stronger the muscles, the stronger and denser the bones will be. This is very important.

Therefore, as we burn more fat, we burn fat more efficiently. As we use our muscles more intensely, we burn more fat. And as we build more and stronger muscle, we burn even more fat even more efficiently, and make the bones stronger.

Different Carbohydrate Intolerance Levels

These mechanisms are universal in animals, but each animal is different, and each person is different. As far as fat loss is concerned, the individuality of people is related to their predispositions to insulin resistance and carbohydrate tolerance, (or actually, intolerance). Every person is differently intolerant to carbohydrates and differently predisposed to insulin resistance.

This is why in a group eating the same diet, there are people who are thin, people who are chubby, people who are fat, and everything in between. Basically, the greater the predisposition to insulin resistance (and the more sedentary), the lower the tolerance to carbohydrates will be, and the fatter you will tend to get. In contrast, the lower the predisposition to insulin resistance (and the more active), the higher the tolerance to carbohydrates, and the thinner you will tend to be.

This translates into different thresholds in the amount of carbohydrate we can eat without negative metabolic consequences, and consequently, the amount under which we must stay in order to burn fat instead of storing it. As a guideline, if you want to burn primarily fat for your body’s energy needs, this threshold would be around 20–25 grams per day if you are fat; around 30–50 gram per day if you are neither fat nor thin, and could be around 80–100 grams per day if you are very thin.

But no matter what your personal threshold happens to be, it will always be the case that the lower the intake of carbohydrates, the lower the glucose and insulin will be, and the more efficiently your body will burn fat as fuel.

Fat Loss Rate

The amount of fat that is burned is determined by the energy balance. The greater the total amount of energy we use, the greater the total energy needs. Total energy needs will mostly be met by energy from food intake and energy from fat reserves. If food energy intake is high, the need for stored energy will be low. If intake is lower, the need for energy from fat reserves will be higher.

Pushing this to the limit—maximal usage of fat stores—we would provide the protein necessary to maintain muscle and other active tissues and nothing more. In this situation, basically all energy needs would be supplied by stored fat reserves and glycogen when needed. This is greatly enhanced by resistance training.

The amount of protein needed is proportional to muscle mass and muscular activity. As a guideline, you can use 1–1.5 grams per kg of lean mass per day in the case of little physical activity, and 2–3 g/kg/d in the case of high muscular activity levels. Excessive protein is not great, but more is almost always better than less.

Fat burning and protein synthesis can be further optimised by intermittent fasting. Extending the time between feedings allows glucose and insulin to drop lower, which increases the rate of fat burning. And by eating fewer but larger amounts of protein in a meal is better because protein synthesis increases in proportion to the amount consumed.

Thyroid function regulates metabolism. Iodine is used in every cell, but in the thyroid, it is concentrated to more than 100 times the average of other tissues, because iodine is the main structural component of thyroid hormones. Iodine supplementation is critical because most soils are highly depleted. It is water soluble and very safe to supplement with.


  • High insulin from carbohydrate intake promotes fat storage.
  • Low insulin from restricting carbohydrates promotes fat loss.
  • Individual predispositions determine the threshold of carbohydrate tolerance.
  • Below this threshold fat is used as the main source of cellular fuel.
  • The rate of fat loss depends on balance between energy needs and energy intake.
  • Maximal fat loss rates are achieved by supplying just the protein needed to sustain lean tissues.
  • Iodine supplementation is critical to healthy thyroid, metabolic and brain function.

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5 thoughts on “Want to lose weight? Here’s what you need to know in under 1000 words

  1. Great post, this is a really succinct introduction to nutrition that alot of people could benefit from, and an awesome reminder of the basic principles to health-conscious people. Greatly appreciated and always looking forward to your material!

    Liked by 1 person

    • Hi Chris, this is not a stupid question at all. In practice it is hard to do, but possible with measurements of various blood markers. To do it in real time, you would have to take measurements of blood glucose and ketones (beta-hydroxy-butyrate). Once in ketosis, you would gradually increase your daily intake of insulin-stimulating carbs, keeping protein and fat equal and activity the same. Then you would monitor BHB to see when you fall out of ketosis. That would be your threshold of glucose. Otherwise, less precise and longer term, you would monitor insulin, HbA1c, HDL, LDL, triglycerides. From the time when you are fully keto-adapted and have these stable (and low), you would increase carb intake. When the curves start to go up, you would know that you have passed your threshold. But this is really long term, and not very precise. Finally, I think the easiest is to monitor your weight (fat loss progress) because it will be proportional to the speed at which you burn your fat reserves. If there is no or very little fat loss, it means you are over your personal threshold.




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