Physiology of Weight Loss

Physiology of Weight Loss

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Welcome to our ‘Weight loss’ section. In here, you will not see any specific diets. However, we will talk about how diets work and what the most common mistakes with them are.

Many people consider weight loss to be a magical process that occurs when you do extensive cardio sessions and eat a lot of salads. And, that’s true, you certainly can lose weight by doing a lot of cardio and eating veggies and fruits, but it’s not a magical (and healthy for that matter) process at all. You can lose weight with ZERO cardio and eating McDonalds too, but that’s not magic either (We’ll cover this later on in the article).

Let’s give a simple run down on how the weight gain/loss/maintenance processes in our bodies work.

The human body, just like every living organism, requires energy to MAINTAIN its body mass. This amount of energy is called “Total Daily Energy Expenditure” (TDEE shortly) and is measured in “Calories”.

Our TDEE is defined by a couple of parameters:

  1. Gender
  2. Age
  3. Weight
  4. Height
  5. Levels of physical activity

Let’s say your TDEE is 2500 calories.

Consume 2500 calories = Maintain body weight

Consume more than 2500 calories (Surplus) = Gain body weight

Consume less than 2500 calories (Deficit) = Lose body weight

So, this is the most basic principle of weight loss- Calories In vs. Calories Out.

If you consume LESS energy than your body requires to MAINTAIN its body mass, you will LOSE weight.

And vice versa- If you consume MORE than your maintenance requirements, you will GAIN weight.

How do I calculate my TDEE?

There are formulas which you can use to calculate your TDEE, but the easiest way is an online calculator, that uses those certain formulas.

What are calories made of?

Calories are mainly made out of the so called ‘Macronutrients’ – Proteins, fats and carbohydrates.

Protein- 4 calories per gram

Proteins are amino-acid chains, interconnected with the so called ‘protein bridges’. Our bodies require proteins for growth purposes. They help with the production of certain hormones, enzymes, anti-bodies and tissues. The presence of certain proteins and their ways of connecting, build the separate tissues and define their properties.

Every protein has its own, unique properties and is responsible for certain bodily needs. Proteins break down into amino acids in our bodies, after which they are used by the organism to recover and create certain protein tissues.

Proteins are found in meat and plants like Soy, peas, beans, lentils and cereals. However, the plants alone do not contain the needed irreplaceable amino acids and despite the high amount of proteins they have, their biological value is not that big.

Animal products like beef, pork, fish, eggs, chicken and dairy products have a significantly higher biological value.

Besides the plastic functions that proteins have, they also stimulate the effect of vitamins and minerals in our bodies, serve as neuro-transmitters and often times are able to neutralize states of depression.

However, you should keep in mind that in big quantities, cure can be poison.

Excessive protein consumption can lead to an overload upon the kidneys and the liver, simply because that’s where the processing of the waste products, from protein metabolism occurs.

Carbohydrates- 4 calories per gram

Carbohydrates are the main source of energy during physical work. They are mostly found in foods of plant origin. Carbohydrates are differentiated in two groups- Simple and complex carbohydrates.

Simple carbohydrates are sucrose (sugar), fructose (Fruit sugar), lactose (dairy sugar). Complex carbohydrates form longer and more complex chains, as they include ballast substances like cellulose, lignin, hemi-cellulose, etc.

The bodybuilding carbohydrate intake is mainly pointed towards complex carbohydrates, due to the fact fibers slow down the sharp increase of blood sugar, limit the insulin interventions and grant a lasting, optimal level of glucose in the blood.

Fats- 9 calories per gram

Fats are the macronutrient with the biggest caloric value.

They are made out of fatty acids- Saturated, unsaturated and polyunsaturated (essential). Fats have various properties. They can also be used as energy, even though that happens slower and more complex, compared to carbohydrates.

The most important property that fats have however, is their participation during the formation of cellular membranes, production of steroid hormones and metabolizing the A, D, E and K vitamins.

Fats, just like carbohydrates must be appropriately dosed, as consumption of excessive quantities, leads the body to storing it as pure fat, that the organism might need to use later on as energy.

Last but not least, for all you night club junkies out there take note of the following.

Alcohol- 7 calories per gram

Organic compounds that contain one or more hydroxyl groups, linked with an aliphatic radicle. Regular, excessive alcohol consumption leads to a psychological addiction.

In bodybuilding, alcohol consumption is looked at as a negative process, especially during the preparation period. That is simply because alcohol contains the so-called “Empty calories”, meaning, it does not contain any nutrients, vitamins or minerals whatsoever. Even more, it ‘helps’ the body during the disposal of many minerals and vitamins like vitamin A, B1, B2, choline, B15, etc.

During the muscle building period, alcohol consumption impedes the metabolism of proteins and carbohydrates.

So, why do “Salads and cardio” diets make you lose weight?

The answer to that question is simple- Cardio makes you burn calories, leading to a higher TDEE. Vegetables are the food with the least caloric value.

To put things in perspective- 1 KILOGRAM of cucumbers has LESS calories than 100 GRAMS of chicken meat. So, it’s really that simple- Veggies, fruits and cardio make it WAY easier to achieve a caloric deficit, without the need to track your calories.

However, is such an approach to nutrition healthy?

These so-called “Fashion model diets” might make you lose weight quickly, but they are CERTAINLY the worst type of diet you can keep.

Why, you might ask? Well, simply because fruits and veggies are NEVER enough, when it comes to a proper balance between all the nutrients that your body requires to keep its physical processes properly running. Yes, they are a good addition to your diet, especially when it comes to food volume- You can stuff yourself with juicy salads to satisfy that hunger and it won’t have that big of an impact on your total caloric intake.

The end goal of weight loss is to look and feel better, right? Then take your time to gradually diet down to your goal look and shape your musculature during the process! (We’re saying look, not weight, because, as cliché as it may sound, weight is just a number that doesn’t really define how your body looks.)

Optimal nutrition

When dieting, we should keep in mind a couple of things:

  1. While in a caloric deficit, our body burns BOTH fat and MUSCLE. The bigger the deficit, the more muscle and fat our body will burn. However, burning muscle is the last thing that we would ever want, so we need to find that ‘Golden deficit’ that will burn the least amount of muscle possible (it’s not possible to completely avoid burning muscle, but through a proper deficit and workout regimen, muscle losses are very little, almost impossible to notice.) This means, we should NOT have an overly big deficit.

Usually, a deficit of 500 calories per day is considered to be the upper limit for healthy weight loss.

1 lb (0,5 kg) of fat = 3500 calories

500 calories of deficit per day, multiplied by 7 days in a week equals 3500 calories of deficit in a week. (500×7=3500) Which means, we will lose a pound (0,5 kg) of fat and muscle in one week, as the bigger part of that pound is fat, due to the rational deficit. So, in other words- Your body uses its energetic stores (Fat, muscle tissue) to compensate for the deficit of calories that you are imposing through your diet.

  1. Macronutrient ratios


Protein intake for beginners, intermediate and advanced athletes is about 1-1, 3g per lbs of bodyweight (2-2, 5g per kilogram). So, if you’re a beginner, intermediate or an advanced athlete that weighs 75 kilograms (165 lbs), your optimal protein intake would be 165~185 grams per day.

For elite athletes, it’s more than 1, 3g per lb (Usually 1.5-2g per lb, or 3.5-4,5g per kilogram). Meaning, if you are a competitive athlete that weighs 100 kilograms (220 lbs), your optimal protein intake forms around 300~450 grams per day.


Your fat intake is usually 0, 4-0, 5g per lb (0.9g per kg) of bodyweight. Meaning, if you are 165 pounds, your fat intake should be around 70 grams per day.


Once you have your required proteins and fats, you can count the rest of your caloric requirement as carbohydrates.

If you have a hard time understanding this, we will build a diet, for a specific individual at the end of this article.

  1. Metabolism

During a weight loss phase (period of time eating at a caloric deficit), our body slows down the metabolism.

Why, you may ask?

When the metabolism slows down, our body manages to quickly store any excess calories as FAT that will serve as an energy source later.

So that’s pretty much what causes the yo-yo effect – After weeks of dieting, we have finally reached our desired shape! Woo! It’s time to binge on crap food again! Well, no… Not really.

If you diet down for a certain amount of time and then quickly get back to eating a $**t ton of food (In a surplus- more calories than your body requires to maintain its weight) your organism will store those excessive calories as fat, because the organism is still EXPECTING to be in a caloric deficit, hence, creating energy stores of fat that it will use to compensate for that deficit later on.

This might sound terrific, but it’s not that hard to avoid. All you have to do is choose the correct post-diet approach to get your metabolism back to normal rates. Read our article on “Reverse dieting”.

So now that you have some knowledge on how to build your diet and what not to do, we can build a diet for a specific individual, using an online calculator.

First off, let’s get the individual’s profile.

Age: 28

Weight: 85 kg

Goal weight: 80 kg

Height: 180 cm

Daily activities: Light (Teacher)

Exercise output: 5 days per week, 60 minutes per day including cardio

Exercise intensity: Moderate- the individual breathes hard and gives themselves a challenge during every workout.

Using an online TDEE calculator for this profile, we have found out that this individual’s MAINTENANCE requirements are 2670 calories per day.

Let’s split that into macronutrients

Protein- 85 kg X 2 = 170 grams of protein a day

Fats- 85 kg x 0.9= 76 grams of fats a day

So, now that we have 170 grams of protein (680 calories) and 76 grams of fats (684 calories), we can calculate the carbohydrates needed, by subtracting the total calories from proteins and fats, from the individual’s TDEE (2670).

Carbohydrates- 2670 – 680 – 684 = 1306 Calories worth of carbohydrates= 327 grams (1306 divided by 4, which is 326.5)

Now that we have the TDEE Macronutrient requirements (170 grams of protein, 326 grams of carbohydrates and 76 grams of fats a day to maintain bodyweight), we can create a deficit, by subtracting carbohydrates, and possibly some fats, but NEVER protein.

Goal weight: 80 kg

Goal deficit- 500 calories

We can sacrifice 6 grams of fats (54 calories) and 114 grams of carbohydrates (455 calories) to achieve the desired caloric deficit.

Daily deficit macronutrients:

170 grams of protein

212 grams of carbohydrates

76 grams of fat

= 2180 calories, which is a deficit of 490 calories.

Weight that will be lost each week- Roughly 0.5 kg

Time required to reach the goal weight of 80 kg- 10 weeks


As a conclusion, we can say that it’s completely possible to lose weight while eating ice cream, McDonalds and other “dirty” foods, as long as you DO NOT EXCEED, but MATCH your daily energy and macronutrient requirements.

However, counting calories can be a pain in the ass at times, and is not really needed, unless you compete, or want to be super strict with your weight loss. So, our advice, from the MeanMuscles team, is to count your calories ONCE or a couple of times, just so you can have an idea of what your food intake, according to your goal should look like! After that, you can simply use your common sense to stick to that diet, without the need to weigh every single bit of food!

Being overly obsessed with weighing your food can certainly lead to an eating disorder, so, as we said, invite your common sense to breakfast, lunch, dinner and other small snacks you might have throughout the day- Enjoy the food you love and don’t restrict yourself from anything. However, do NOT overeat and have your limits with everything!

In case you have found out your individual macronutrient needs, but have a hard time choosing foods, check out our FOOD CHART by clicking HERE.

It contains our top picks of foods for each macronutrient, as well as a page with nutritional information for most of the foods you consume on a daily basis.

Stay healthy!



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