Calorie Deficit: Don’t Harm Hormonal Mechanisms

calorie deficit

As you may probably know, losing weight takes not only your fat storages, muscles, and calorie intake but also harms your hormones. Here you’ll see how not to ruin your health and build a good calorie deficit.

What is Calorie Deficit

The golden rule for losing weight is a calorie-deficient diet. What does it mean? Speaking in a simplified language, you should consume less food than you manage to spend during the day. Roughly speaking, everything that the body did not to convert into energy is deposited on our body in the form of fat. With a nutritional deficiency, the body has to look for additional sources of energy, and it begins to let fat cells into consumption.

The calorie deficit is calculated relative to the daily calorie intake. You can find a calorie deficit calculator and formulas which can help you.

What calorie deficit do I need

calorie deficit calculator

But the question remains, how large a calorie deficit is needed for effective and safe weight loss? We recommend sticking to 20% and, in no case, lower the calorie corridor below the 30% deficit. Accordingly, with average parameters (age 35 years, weight 70 kg, height 170 cm, medium activity), the corridor will be 1500-1600 kcal with a deficit of 20%.

Accordingly, if you decide to start losing weight, we recommend using a 20% deficit. If you want to speed up the process of losing weight a little, then take a calorie deficit of 20-30%, but never fall below this line. Once you are close to your desired weight, you can gradually increase the daily calorie intake, reducing the deficit.

How Can it Harm Hormonal Background

The limitation of caloric intake causes changes in the level of a number of hormones and neurotransmitters and the lower the percentage of fat in the body, the faster the whole chain starts (the process shown is more or less made by wide strokes, for a general understanding of the processes step-by-step):

  1. first decreases the level of a hormone that stimulates the formation and secretion of thyroid hormones, luteinizing hormone and follicle-stimulating hormone (TSH, LH, and FSH, respectively);
  2. the level of thyroid hormones and testosterone (estrogen) decreases;
  3. the level of the factor releasing growth hormone (somatocrinin) decreases;
  4. appears a negative effect on the secretion of growth hormone;
  5. the activity of the sympathetic nervous system decreases, which, together with a decrease in the level of thyroid hormones, significantly reduces the metabolic rate;
  6. the level of cortisol rises, hunger and appetite increase;
  7. changes in the levels of leptin, ghrelin, YY peptide, corticoliberin (corticotropin-releasing hormone) (and a number of other hormones) take place;
  8. leptin falls (less fat in the cell, less leptin is produced), dopamine falls (responsible for pleasure);
  9. neuropeptide Y is produced (which is produced under conditions of hunger, that is, less leptin – more than neuropeptide Y, that is, the brain gives the command to “eat”).

These changes “tell” the brain that food is not enough, which ultimately causes changes in neurotransmitters that stimulate a certain number of negative adaptations. This process, of course, takes some time and does not occur instantly. That is, there is a certain gap between the changes in all these hormones and the reaction of the body.

Side effects of calorie deficit

calorie deficit diet

Against the background of all the changes taking place, many other adaptation processes are taking place, for example:

  • a drop in the level of leptin directly affects the metabolism in the liver, skeletal muscles and cells, mainly for the worse;
  • testosterone binds to androgen binding globulin and the level of free testosterone decreases (this is in addition to the fact that testosterone levels generally decrease);
  • insulin levels are reduced (which is an anti-catabolic hormone and prevents muscle breakdown);
  • cortisol levels increase (cortisol enhances protein breakdown and stimulates the production of glucose from the protein in the liver);
  • depletion of energy reserves in the muscles prevents the synthesis of protein, although it contributes to the oxidation of fats;
  • protein synthesis slows down, and its cleavage is accelerated, which leads to muscle loss;
  • the increased level of fatty acids in the blood helps the liver absorb T4 hormone (thyroxine, the “passive” form of the thyroid hormone), and changes also occur during the conversion of T4 to T3 (the “active” form of the hormone, triiodothyronine) in the liver;
    • decreases the level of the hormone T3 in the blood;
      • an increase in the level of fatty acids in the blood causes resistance to the thyroid hormone in the tissues.
  • corticoliberin levels increase
    • the level of luteinizing hormone and follicle-stimulating hormone decreases – TSH, LH, and FSH (stimulating the formation and secretion of thyroid hormones)
      • the level of thyroid hormones and testosterone (estrogen) also decreases
        • growth hormone secretion decreases (somatocrinin)
          • the activity of the sympathetic nervous system decreases, changes in metabolic processes in the liver also negatively affect the conversion of growth hormone into an insulin-like growth factor

Chronically elevated cortisol on a diet, in addition to retaining water, also causes leptin resistance.

After 3-4 days, the activity of the nervous system decreases on a diet – metabolism slows down.

Why our body prevents us from fat burning


All these adaptation changes are for two basic goals:

The first goal

A slowdown in the rate of burning fat, which should allow you to survive as long as possible. For this, the body also reduces all types of activity that require energy. This includes protein synthesis, reproductive and immune functions; because there is no use in these functions when you die of hunger. All these hormonal changes, starting with a drop in leptin levels, are the main reasons why men lose their sex drive (and opportunities), and women stop menstruating when they reach a very low percentage of fat / or are on a strict diet.

The second goal

The main thing for your body is to replenish fat stores as soon as possible when calories are available again. Slowing the metabolic rate and improving the ability to accumulate fat combine to promote the return of body fat when you start eating again. The combination of signals sent by leptin, ghrelin, insulin, glucose, and a host of other hormones (cholecystokinin, glucagon-like peptides 1 and 2, bombesin, and many others) turns into hunger and appetite. These changes cause an increase in both: you are constantly hungry and constantly thinking about food.

How to Determine a Decrease in Metabolic Rate and the Level of Its Decline?

Method #1.

You can preliminarily try to focus on the indications of the autonomic nervous system, specifically the sympathetic and parasympathetic (the sympathetic nervous system is responsible for enhancing metabolism, increases the excitability of most tissues, mobilizes the body’s energy for active activity; the parasympathetic nervous system helps to restore the expended energy reserves, regulates the vital activity of the body during the time to sleep).

If the activity of the sympathetic system decreases, and the parasympathetic system, on the contrary, then it most likely means a slowdown in metabolism.

Method #2.

It is possible to determine the current state of metabolic rate as the current temperature readings (somewhere a decrease of 0.5-0.6 degrees Celsius = 10% decrease in metabolism. The lower bar, most likely not lower than 35.5C (this will be – 20% ). Below 35 degrees Celsius, this is already pathological changes in the direction of death.

Corresponding study – Rising R1, Keys A, Ravussin E, Bogardus C. Concomitant interindividual variation in body temperature and metabolic rate. Am J Physiol. 1992 Oct;263(4 Pt 1):E730-4.

Method #3.

Get tested.

  1. Blood biochemistry (in principle, it doesn’t make much sense to do it often if everything in the body is in order that is, it is made every six months), and the next:
    • urea in the blood to determine the digestibility of the protein;
    • AST, ALT, bilirubin – to know the condition of the liver;
    • prothrombin index, LDL, HDL – to protect yourself from plaques and blood clots in blood vessels.
  2. Before a diet for weight loss, it is better to pass on hormones (it is more correct to get tests before starting a diet and a couple of times during it):
    1. Testosterone (general). Should not fall too much from the initial value (before the diet);
    2. Leptin. Should not fall too much from the initial value (before the diet);
    3. Cortisol. Should not fall too much from the initial value (before the diet);
    4. Free T4, free T3, look at their ratio: low T3 at high T4 indicates a poor conversion of T4 to T3. It’s useless to eat T4;
    5. Estradiol. The optimal level for the weight loss should be in the lower half of the reference values (for men: it is good to grow muscles on relatively high estradiol, but the level should rather be slightly higher than the average of the reference values);
    6. Progesterone. The lower it is, the worse it is for the torching fat (its decrease indicates in favor of a decreased metabolism). It should be borne in mind that high levels of this hormone in men, in the region of 2 nmol / L, are the main marker of overtraining; in women, this may be very low levels of estradiol;
    7. Prolactin. Should not be in the upper half of the reference values, as with high prolactin, fat is reluctantly torched;
    8. Besides testosterone and other hormones of the reproductive group, you can get: luteinizing hormone (LH), follicle-stimulating hormone (FSH), sex hormone-binding globulin (SHBG).
Recommendations for routine screening for the female gender
  • Luteinizing hormone (LH) is given on an empty stomach, on 2-5 day from the beginning of menstrual bleeding. 3 days before taking blood, it is necessary to exclude sports training. 1 hour before taking blood – to eliminate smoking;
  • FSH is taken on 2-5 day from the onset of menstrual bleeding (this is the 1st phase of the cycle) with a 28-day cycle;
  • Testosterone is taken on 2-5 day from the onset of menstrual bleeding (this is the 1st phase of the cycle) with a 28-day cycle;
  • Free testosterone, is taken on an empty stomach;
  • Progesterone is taken on an empty stomach, on the 22-23 day of the menstrual cycle;
  • Estradiol is taken on 2-5 day from the onset of menstrual bleeding (this is the 1st phase of the cycle) with a 28-day cycle;
  • Prolactin is taken the day before the study. Exclude sexual contact and thermal effects (sauna, hot bath), exclude smoking 1 hour before the test. Since stress situations have a great influence on prolactin levels, it is advisable to exclude factors that influence the research results:
    • physical stress (running, climbing stairs),
    • emotional arousal,
    • drinking alcohol.
      • Blood for prolactin must be screened no earlier than 3 hours after waking up. Before the procedure, you should rest 10-15 minutes in the waiting room and calm down.

It is advisable to undergo an ultrasound of the pelvic organs if there are any deviations according to the analysis.


  1. L.McDonald. Another Look at Metabolic Damage.
  2. L.McDonald. Determining the maximum dietary deficit for fat loss.
  3. Robert M. Sapolsky. Why Zebras Don’t Get Ulcers

Additionally, see how to do complete breaks on a calorie deficit diet.

What is more, find out the top 5 myths about chicken eggs.