When it comes to losing weight, the first advice a person comes up with is “cut your carbs.” A low carbohydrates diet does help you lose weight—it’s an easy way to cut calories by cutting out bread, pasta, pastries, and sugar.
But does it help you lose weight faster? In the long run, there is no difference between a low-carb diet and a moderate-carb diet. Long-term carb restriction (less than 100 grams per day) can cause more problems than good.
Low carb diet and adrenal glands
Three main glands produce hormones that control the entire body:
- Hypothalamus: Located in the brain.
- Pituitary gland: also in the brain.
- Adrenal glands: located at the top of the kidneys.
They all interact with each other to keep hormones in balance. This is known as the hypothalamic-pituitary-adrenal axis. It is responsible for managing stress, mood, emotions, digestion, immunity, libido, metabolism, and more.
The glands are sensitive to the number of calories from food, stress, and physical activity. Long-term stress, a starvation diet, or excess exercise (and very often, this comes with losing weight in the kit) lead to an increase in the level of stress hormones. This creates an imbalance throughout the system, sometimes referred to as “adrenal fatigue” ( 2, 3 ).
Among the symptoms are constant physical fatigue and loss of strength, especially in the morning, weakening of the immune system, and frequent acute respiratory infections. As well as a higher risk of long-term problems – such as hypothyroidism, exacerbation of chronic diseases, diabetes, and depression.
A diet too low in calories and carbohydrates is stressful for the body and causes glandular dysfunction. Additionally, some research suggests that it may increase cortisol production, exacerbating the problem ( 4, 5 ).
Rising cortisol, falling testosterone
Studies show that people who exercise regularly need to eat enough carbohydrates, or their testosterone levels will drop, and their levels of the stress hormone cortisol will rise. This is a guaranteed recipe for losing muscle and gaining visceral fat (in the abdomen, around the organs).
The same thing (an increase in cortisol, a decrease in testosterone) also occurs with long, excessive training, when the body does not have time to recover and is depleted.
When we think of muscle growth, we usually think of protein. But research shows that reducing carbs can affect muscle mass, even if you get enough protein. In other words, even if you gorge on protein shakes five times a day, you may not grow your muscles if you don’t get enough carbs. Insulin is important for muscle growth. When you eat enough carbohydrates to replenish muscle glycogen, this creates an anabolic hormonal environment.
When you don’t get enough carbs, muscle glycogen gets depleted, and your hormones become catabolic, which means more protein breakdown and less synthesis.
Low-carbohydrate diet and cycle disorder in women
Refusal of carbohydrates in a calorie deficit can lead to hormonal disruptions in women. It is assumed that a woman’s body is more sensitive to a low level of calories in food and a percentage of body fat.
The hypothalamus and pituitary gland, located in the brain, are extremely sensitive to things like energy availability and stress (this includes psychological stress and starvation, diet, and strength training).
Quite common is the so-called hypothalamic amenorrhea, that is, the absence of menstruation caused by a large restriction of calories and carbohydrates, sudden weight loss, a decrease in the percentage of body fat to a minimum level, stress or excess physical training ( 6 ).
So for example, many women who are professional bodybuilders suffer from cycle disorders during extreme training regimens for competitions.
This is due to falling levels of various hormones, including gonadotropin-releasing hormone, which kicks off the menstrual cycle ( 7 ). This leads to lower levels of other hormones—luteinizing hormone (LH), follicle-stimulating hormone (FSH), estrogen, progesterone, and testosterone ( 8 ).
The amount and type of carbohydrates consumed are related to a woman’s ability to conceive. So, high and very low carbohydrates are associated with reduced fertility ( 16 ).
Continued severe carbohydrate reduction can disrupt hormone levels, causing amenorrhea or an irregular menstrual cycle that reduces a woman’s ability to conceive ( 10, 17, 18, 19 ).
Low leptin levels cause amenorrhea and menstrual irregularities ( 9, 10 ).
Leptin is a hormone produced by the body’s fat cells communicating with the brain. Leptin tells the brain about how the body is doing with energy reserves. When there is a lot of leptin, the brain understands that there is enough fat (energy) in the body, so it makes no sense to replenish its reserves urgently. When leptin is low, it signals to the brain about hunger and the risk of death. As a result, it reduces metabolism and increases the feeling of hunger.
Severe calorie reductions, especially carbohydrates, can lower leptin levels and interfere with its ability to manage reproductive hormones. This is especially true for women who are very thin or extremely thin on a low-carbohydrate diet ( 11, 12 ).
Low carb diet and thyroid
The thyroid gland produces two hormones: thyroxine (T4) and triiodothyronine (T3). These hormones are essential for various bodily functions: breathing, heart rate, nervous system function, metabolism, weight control, temperature control, cholesterol levels, and the menstrual cycle.
T3, the active thyroid hormone, is very sensitive to calories and carbohydrate intake. Suppose both are too low, and their level drop ( 13, 14 ). This can slow down the metabolism, which causes weight gain, increased fatigue and feelings of fatigue, decreased concentration, depressed mood, and more.
Carbohydrates and immunity
A carbohydrate deficiency, especially when combined with strength training, can lead to reduced immunity, which increases susceptibility to disease. That is why many who combine a low-carb diet with hard workouts and tons of cardio often get colds. And beside them, against the background of a decrease in immunity, allergic reactions and various chronic diseases can worsen.
Glucose is an important fuel for cells of the immune system – lymphocytes, neutrophils, and macrophages. The immune system cells have a high metabolic rate, which explains the importance of adequate nutrition for their smooth operation.
Cortisol has anti-inflammatory (immunosuppressive) properties, reducing the level of lymphocytes, and lymphocytes are the main cells of the immune system.
It depletes the amino acid glutamine, breaking it down for energy for the CNS without glucose. Glutamine is the main building block of the immune system. Without it, the immune system loses its ability to produce antibodies, lymphocytes, leukocytes, cytokines, and other cells. As a result, the body is less able to resist infections.
Carbohydrates, mood, and sleep
A carbohydrate deficiency in the diet reduces the production of the neurotransmitters serotonin and dopamine, which is associated with high levels of stress, depression, anxiety, and irritability.
A high-carb dinner or high-glycemic carbohydrates eaten a couple of hours before bed can help you fall asleep faster and improve sleep. It is also associated with an increase in the level of serotonin, which not only has the properties of an antidepressant but is also a building block for the “sleep hormone” melatonin. Carbohydrates also help penetrate the amino acid tryptophan into the brain. It is involved in the formation of serotonin.
Some people who train hard and cut carbs in the evening suffering from insomnia. Now you know why. If you’re having trouble sleeping, it may be worth shifting most of your carbohydrates from your morning or afternoon meal to your evening meal (while maintaining your overall calorie deficit and carbohydrate intake).
How much do you need?
The optimal amount of carbohydrates is different for each person. For most women on a diet, this is about 100-150 grams daily, but it is not recommended to go below 100 – this is how much glucose the brain consumes per day ( 20, 21 ).
Some women on a diet require more carbohydrates (150-200 and above), especially if there is any of the following:
- Intense and frequent workouts.
- Reduced thyroid function (with a doctor’s consultation and medication, if necessary).
- Irregular cycle or lack of it.
- Low carb diet for a long time.
- Sleep problems.
- Pregnancy or breastfeeding.
Some women should choose a low-carb diet (but preferably not go below 100 grams per day) if they have any of the following: