What Happens to Your Body if You Don't Eat Dinner?

If you don't eat dinner, a series of physiological adaptations will take place in the internal environment that can be positive. Learn more.

Written and verified by el nutricionista Saúl Sánchez.

Last update: 26 December, 2022

If you don’t eat dinner, a series of physiological changes may occur in your body that will have an impact on your health. Now, it isn’t necessarily bad as such, as long as it takes place within a proper context. Be that as it may, knowing the effects will be decisive in order to know in which situations this meal can be avoided and when it can’t.

Not having dinner can be considered part of an intermittent fasting protocol, a strategy that has become very trendy in recent years. It has become popular above all for its power when it comes to improving the state of body composition, especially in people with metabolic disorders.

The use of energy substrates if you don’t eat dinner

When you don’t eat dinner, glucose manufacturing processes in the liver soon start up. It may be synthesized from fatty acids and amino acids, a process known as gluconeogenesis. Therefore, when blood sugar levels drop, this class of mechanisms is activated in order to maintain homeostasis in the internal environment.

But at the same time, the production of ketone bodies may increase, especially to guarantee the cerebral energy supply. Under fasting conditions, these compounds are the main energy substrate for the brain, while glucose is distributed throughout the tissues.

Of course, if enough hours go by without eating, muscle and liver glycogen stores could be depleted, something negative if the intention is to perform physical activity the next day.

Hormonal changes

One important consideration must be taken into account. When you don’t eat dinner, a series of alterations in the hormonal balance are experienced to avoid the degradation of muscle proteins, which would lead to catabolism, which isn’t very positive for health.

As a general rule, what happens is that the synthesis of growth hormone increases. But in this case, it doesn’t have anabolic functions, but rather, anti-catabolic ones. As long as the fasting situation doesn’t last for more than 24 hours, lean tissue proteins will be spared as much as possible.

Taking these considerations into account, we can deduce that during the overnight fasting period, the oxidation of fatty acids is prioritized as a source of energy. Thanks to this, you can experience weight loss in the medium term.

In fact, there’s evidence that intermittent fasting protocols can be positive for this, as long as an energy deficit is established. However, it’s not advisable to consider a very strict diet in terms of caloric intake, as it could become unsustainable.

The benefits of overnight fasting

In addition to the physiology discussed, other positive effects can be experienced if you don’t eat dinner. In many cases, the intake of simple sugars at night is considered especially harmful. Or even carbohydrates as such, when we talk about sedentary situations and people with a genetic predisposition toward metabolic disease. A study published in the journal Nutrition & Diabetes confirms this.

On many occasions, carbohydrate management is more efficient when they’re included in the regimen during daylight hours. Therefore, it affects glucose homeostasis. When it gets out of control, it could end up leading to chronic and complex diseases in the medium term, such as type-2 diabetes, mainly in people who don’t perform intense physical activity.

When we introduce strength training into the equation, the situation varies substantially. In this case, the muscle acts as a balance point, improving insulin sensitivity and preventing inefficiencies in the use of carbohydrates by cells and mitochondria.

In fact, when the level of exercise is high, it could even be advisable to consume a large amount of carbohydrates at night to avoid negative changes in performance.

Is it bad to go without dinner?

In general, it shouldn’t be a bad thing to go without dinner, as long as you don’t experience appetite and this doesn’t negatively affect compliance with and adherence to your diet.

If you suffer from anxiety problems, you’ll need to follow another protocol that’s more suited to the individual conditions of each person, which will allow you to follow it in the medium term and experience positive effects from there.

Now, if you don’t eat dinner, you have to ensure that protein consumption during the rest of the day is adequate, thus managing to cover the requirements. These are at least 0.8 grams of protein per kilo of weight for sedentary people, but they can easily double in athletes. This is evidenced by research published in the Annals of Nutrition & Metabolism.

In this way, lean tissue will be protected and muscle protein breakdown will be prevented from exceeding synthesis during the day, which could end catabolism. From here, it would be likely that a complex disease known as sarcopenia could be experienced over the years.

This involves a progressive loss of strength and increases the risk of death from any cause. A study published in Peritoneal Dialysis International corroborates this.

Of course, when the consumption of nutrients during the rest of the day is optimal, following an intermittent fasting protocol can be quite positive in certain cases. For example, it has been shown that it promotes mitochondrial biogenesis, a determining process to improve the efficiency of metabolism and avoid the development of complex diseases.

Is it better not to have breakfast or not to have dinner?

Intermittent fasting protocols can actually be approached in several different ways. The most common is not having breakfast or not having dinner, being also the most comfortable. From the point of view of physiology, it would be difficult to say which is better. Both alternatives can be good if effective caloric restriction is achieved, especially regarding weight loss and autophagy.

For many people, it’s easier to avoid breakfast than dinner. This simply occurs because late in the day, your appetite tends to increase, and just the opposite occurs after waking up. We’re talking about a sensation that can be modulated by circadian hormonal secretion, so it will also present an important individual component.

In this case, the most convenient thing is to adapt the protocol to each person. Thus, greater adherence is achieved and it is maintained over time, extending the benefits.

At the end of the day, the determining factor is to achieve a balance or slight energy deficit, apart from promoting other good lifestyle habits. Thanks to this, in the medium term, it will be possible to optimize your state of health as well as your body composition.

Can you do sports in the morning if you don’t have dinner?

One thing with which some care must be taken is the practice of sports on an empty stomach if there was no dinner the day before. Some people will get used to it quickly and it won’t be too much of a problem, but it’s normal for performance to be significantly degraded.

Exercise is usually quite dependent on glucose and glycogen when performed at a minimum intensity. Starting without full nutritional stores could lead to the onset of early fatigue.

At the same time, we’ve mentioned that up to the first 24 hours of fasting, the body generates a series of adaptations to avoid catabolism of lean mass. However, when we include the physical activity variable, this can be altered.

If the energy demands are very high, muscle protein amino acids will begin to be used for energy synthesis with the aim of satisfying the new needs.

For this reason, in the case of exercising on an empty stomach after a night without dinner, it’s best to greatly modulate the level of intensity. You should always practice below 70% of the maximum, prioritizing resistance work that’s not very long. Therefore, a series of adaptations could even be experienced that would be good for the state of body composition or for sports physiology in the medium term.

Adaptations to fasting training

Under fasting training conditions, the use of fat as an energy substrate tends to increase, which gradually improves the efficiency of said process. According to a study published in Sports Medicine , the metabolism is usually altered during sports practice in periods of fasting, so the loads will also have to be adapted to avoid possible injuries or drops in performance.

But you always have to keep in mind that there’s an important genetic component to all of this. Depending on the person, performance may be more or less altered under such circumstances. In the end, the key is to adapt to individual contexts and the preferences of each person, thus ensuring that the established protocols are maintained over time.

If you don’t eat dinner, the physiology of your body is altered

If you don’t eat dinner, certain aspects of the physiology of the internal environment may be altered. Now, this doesn’t have to be a negative thing. Rather, the opposite occurs when the intermittent fasting protocol is included in your routines with good judgment. For this, it may be necessary to consult a professional in order to achieve a better adaptation and extract the maximum possible benefits.

Finally, keep in mind that depending on people’s work routines, the option of not having dinner may or may not exist. In the case of night workers, it’s usually complicated. If you want to implement intermittent fasting in this kind of situation, you’ll have to opt for a different distribution of meals, as at night, your appetite may increase and it will be more difficult to endure without eating.