Five reasons why you get fat

07 January 2021
Antonio Ciociaro
Edited by Antonio Ciociaro


There are many reasons for weight gain, but in the absence of established pathological causes, the first reason can only be a calorie intake that exceeds our energy requirements. In fact, if we tend to consume more calories than necessary to maintain vital functions for longer or shorter periods, we will almost inevitably tend to gain weight. To simplify, we could say that:

  • Calories introduced equal to those consumed = stable weight
  • Less calories introduced than consumed = weight loss
  • Calories taken in excess of those consumed = weight gain

This is increasingly likely to happen as the years go by, when the basal metabolic rate physiologically tends to drop. However, the high rate of childhood obesity should make us reflect on how metabolism is only a small component of the whole system, so the excuse "I get fat because I have a slow metabolism" does not apply. You can overcome this obstacle with the next key point.



The second reason, closely related to the first, is physical inactivity. A life that is too sedentary encourages the accumulation of fat mass because the excess calories consumed are not spent on the musculoskeletal system. Moreover, physical inactivity encourages the loss of muscle tone, which is the metabolically active tissue of our body, so the less we move, the more difficult it will be to lose weight and the easier it will be to regain it after a diet unaccompanied by physical activity.

Be careful, physical activity does not mean becoming an athlete, but doing something suited to the person and the diet you are following will maximise results and, not least, have major benefits from a cardiovascular and psychological point of view. Paying attention to your energy intake and moving more can solve most of the problems of overweight and obesity, but it is clearly advisable to consult a specialist who can guide you through the weight loss process.



An unbalanced diet that can easily lead to weight gain almost always includes energy-dense foods that do not contain fibre and nutrients useful to the body, but sugars and saturated fats, which, while not to be eliminated entirely, should be severely limited. Fast food, sweets, crisps, nuts, chocolate, alcohol, biscuits, etc. are undoubtedly foods with a high palatability, but they have the big problem of not being satisfying and of supplying our bodies with excess nutrients.

No food is to be demonised or eliminated from our diet, but it is important to be aware that some foods, for the same weight, are much more calorific than others without being able to give the sense of satiety. It seems obvious, but in a well-crafted diet it feels like you are eating more despite the fact that, calorie-wise, this is not the case at all. This is because choosing fresh foods, with higher water and fibre content, leads to a different result in terms of satiety.



Stress, little rest, and consequently high levels of the stress hormone cortisol are negative conditions that greatly influence our habits, including nutrition. It is well known that chronic stress stimulates the production of hormones and other substances that work against slimming processes and, on the contrary, promote the accumulation of fat.

People who are constantly under stress will be more likely to channel their bad moods into food and increase their caloric intake, which will lead to weight gain. Poor quality and quantity of sleep also negatively influences metabolic processes by, among other things, increasing the production of cortisol. Sleeping little and badly makes us less productive during the day and, above all, less active, both for work and for exercise, which, as we have already said, is essential for weight management. This is to say that weight gain is primarily due to excess calories and lack of physical activity, but behind this there can be many factors (including hormonal factors) that favour this combination and that are part of the overall lifestyle management.



A good opportunity to gain weight is classically after an overly restrictive diet that initially leads to losing a lot of kilos in a short time and then regaining them with interest. This is due to a number of factors, first and foremost because losing weight quickly through unbalanced and restrictive diets, perhaps through prolonged fasting, leads to a loss of fluid, muscle mass with little involvement of fat mass: this leads to a drop in metabolism and a kind of energy-saving mode for our bodies. Once you resume eating normally or even more (food deprivation leads to revolt, usually the more rigid and restrictive the diet, the more our body will require all the food we have unnecessarily deprived ourselves of or cut back sharply on) you will tend to gain weight afterwards, especially after a period when calories have been too low and the wrong body components are lost.  So, one reason for getting fat is to have done unbalanced diets that lead to damage not only on a physical level but also on a psychological level, and we have seen how closely all this is related.

These are the 5 most common and relevant reasons that cause weight gain, I have voluntarily excluded pathological conditions such as hypothyroidism and insulin resistance that can facilitate weight gain (facilitate, not cause it all the time) but should absolutely be treated in collaboration with a doctor specialised in metabolic diseases such as endocrinologist.