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10 reasons why you can gain weight while watching your diet

Are you putting on weight for no reason, even though you are trying hard to watch your diet? This is normal. It seems unfair when you don't know ALL the things that can affect your weight. This (non-exhaustive) list refers to all the explanations linked to this sometimes very frustrating phenomenon.

1. Caloric intake too high in relation to needs

In dietetics, we work on the common basis of a daily calorie requirement of 2105 kcal for a woman (aged 20 to 40 with average physical activity) and 2600 kcal for a man (aged 20 to 40 with average physical activity).

This is a rough estimate that is found on the nutritional value tables on food packaging.

As you will have understood by now, this figure is only indicative and true for a small part of the population. The caloric requirement (i.e. what you need to eat to meet your needs and therefore not gain weight) is individual and depends on many factors such as age (exact and not a range), weight and physical activity. It is essential before any weight loss initiative to have a professional estimate YOUR daily caloric needs.

Because you will learn that it is enough to take in just a little more than you need, but consistently (every day), to cause real weight gain.

2. Incorrect distribution of nutrients (Protein / Carbohydrates / Fats)

A diet that favours carbohydrates (=sugars) to the detriment of proteins (animal OR vegetable) will inevitably result in a loss of muscle mass.

However, loss of muscle mass is always accompanied by a reduction in daily caloric requirements and therefore in energy expenditure at rest.

In dietetics (always), we are able (via a learned calculation that I will spare you), to evaluate what is called the basic metabolism.


Basal metabolic rate : This is the amount of energy measured experimentally in an individual who has been fasting for more than 12 hours, is lying down, has been resting for 2 hours, is awake, is emotionally calm, and is in a zone of thermo-neutrality (outside temperature of approximately 22°C for a clothed, lying subject).


In short, this is the number of daily calories that you consume without doing anything. And the poor distribution of nutrients in a day will lower this value.

Moreover, the loss of muscle mass is generally accompanied by a high level of fatigue which is compensated for by a (poor) intake of food rich in sugary products or too many calories. It is therefore essential to be guided in the amount of protein, fat and carbohydrates that you should ideally consume per day.

3. Decreased physical activity

You've always been quite active, but over time you've traded in walking for driving and evenings at the gym for movie nights. This is not a crime in itself, but this change in lifestyle is rarely followed by an adjustment in eating habits.

However, when physical activity decreases, your muscle mass is reduced: you burn fewer calories at rest. You should therefore naturally reduce your food intake, which is rarely, if ever, the case.

If you continue to consume as many calories as before, the excess energy will inevitably be stored in the fat cells (adipocytes) and you will gain weight.

4. Lack of sleep

According to various experimental studies, sleep deprivation, even for only a few days, has a very negative effect on our body and in particular on the production of 4 hormones involved in weight regulation :

- Cortisol : the stress hormone that increases appetite, especially for comfort foods such as sweets. This hormone also has the power to slow down the power of another hormone, insulin. Faced with this lack of efficiency, insulin production will naturally increase...

- Insulin : the storage hormone that stimulates the entry and retention of fat in the adipocytes. The more insulin you produce, the more "fat" you store.

- Ghrelin: the hunger hormone that manages the feeling of hunger. In case of disturbed sleep, ghrelin is produced in excess, and generates a feeling of excessive hunger without it really being real.

- Leptin : the satiety hormone that manages the feeling of fullness. During a lack of sleep, its production decreases and you are totally disconnected from the feeling of satiety. You eat without hunger.

5. Amount of stress

Stress is a vast subject. As you can see in the previous point, stress has a negative impact on the production of cortisol, the prolonged secretion of which will cause various metabolic disorders leading to weight gain:

> It sends a signal to fat cells (adipocytes) to store fat without releasing it.

> It promotes fat storage through its insulin inhibiting effect

> It stimulates the intake of food associated with comfort (sugar, fat, alcohol)

> It interferes with serotonin (= mood neurotransmitter), which is involved in the food drive.

> It interferes with the effects of leptin, which is involved in the feeling of "not being hungry".

> It interferes with growth hormone, which is essential for maintaining muscle mass.

6. Some medicines

Some medicines have a side effect of weight gain. But you need to know about them.

> Antibiotics disturb the balance of the intestinal microbiota (= all the micro-organisms - bacteria, micro-fungi - living in the digestive system), which is particularly involved in energy metabolism and weight regulation.

> Corticosteroids, used to treat inflammatory and autoimmune diseases, promote the appearance of oedemas (water and sodium retention), and lead to the redistribution of fat.

> Neuroleptics (or antipsychotics) -> bipolar disorders

> Antihistamines -> against allergies

> Anti-epileptics -> epileptic disorders

> Antidepressants -> for depression

>> All these drugs act on the brain, causing a disruption of hunger and satiety signals.

7. Quitting smoking

Weight gain during nicotine withdrawal is not a myth. When you smoke, the nicotine contained in tobacco acts by reducing your appetite, increasing your energy expenditure and slowing down the storage of fat. In short, it becomes an "appetite suppressant" that disappears when you stop.

Addiction to the gesture is often compensated by snacking.

Smoking generates a considerable loss of tastes and smells which, once returned during withdrawal, will induce a little more greed on the part of the former smoker who is used to having almost only the taste of tobacco in his mouth.

All these factors will facilitate weight gain (5kg on average). This consequence, which occurs during the first few months of withdrawal, should not be an obstacle to stopping smoking. It is just advisable to change other elements of your daily life during the withdrawal period.

8. The intestinal microbiota

As stated earlier, the microbiota (=also called "intestinal flora") is the set of (good) bacteria that thrive in your digestive system and more particularly in the intestines. A good microbiota allows you to recover energy from food in the best possible way. But when the composition of the microbiota is altered, it is no longer able to regulate this constant influx of energy correctly and an imbalance is guaranteed.

The microbiota controls our hunger and mood via signals sent by our brain, liver and fat cells.

And there are many causes for the alteration of the intestinal flora:

> Stress : reduces the volume & quality of digestive juices (essential for digestion/absorption)

> Sugar : acts as an "acid" by destroying the (good) bacteria of the intestinal flora

> Food additives : chemical substances and/or preservatives that continue to act in our intestine and disrupt the microbiota in a very important way

> Chlorine : present in tap water to disinfect it will continue to act on the bacteria once ingested and thus exterminate all the useful bacteria in our body.

> Fluoride : present in some toothpastes can alter the composition of the oral microbiota and in small doses the intestinal microbiota

> Pesticides & insecticides : present on fruit and vegetables

> Viral infections (gastroenteritis)

> Antibiotics : destroy ALL bacteria whether they are harmful or necessary

> Chronic use of drugs that have a negative effect on the intestinal tract

Non-steroidal anti-inflammatory drugs (NSAIDs): acetylsalicylic acid (Aspirin®, Aspegic®...), Diclofenac (Flector®, Voltaren®...), Ibuprofen (Advil®, Nurofen®...), or Ketoprofen (Profenid®, Kétum®...).

Paracetamol is NOT a member of the NSAID family, although they share some indications.

Oral contraceptives

> Chronic alcohol use

9. Hypothyroidism

The thyroid produces hormones involved in the regulation of energy metabolism. In hypothyroidism, these hormones are produced in insufficient quantities, leading to a decrease in energy expenditure at mealtimes (see: basic metabolism).

The body therefore functions at a slower pace with the most common symptoms being

- fatigue

- depression

- drowsiness

- constipation

- coldness


Although it is not very common in women who are in good health, thyroid dysfunction is quite common in menopausal women. A thyroid check-up is recommended in order to be sure and to agree on a suitable diet and supervised medication, without which weight gain is almost inevitable.

10. Menopause

The menopause is a natural stage in the life of a woman of about 50 years. The age at which it occurs varies from one woman to another but the associated symptoms are often the same and weight gain is one of them. The menopause is a period of hormonal changes leading to major physiological and physical changes.

These changes include loss of muscle mass, hormonal imbalance, weight gain (between 5 and 7kg) and resistance to weight loss.


Being overweight is not inevitable, but to lose weight effectively, if you are in one or more of the above situations, you should

>> Identify the cause of your weight gain with the help of a health professional (especially for possible blood tests: insulin, cortisol, sex and thyroid hormones)

>> Follow a complete and personalised programme

>> To be accompanied on a regular and individual basis by a dietician

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