Avoiding food after 6 PM (skipping dinner) is a common practice among people trying to lose weight or maintain current one. Advocates of this habit claim that late food intake results in fat tissue storage because the body does not need food at that time due to lower levels of activity.
First thing that pops into my mind is – Why 6 PM? Why not 7 PM? What if I wake up at noon? What if I train at night? What if I work night shifts? Etc. These questions already suggest that something is not quite right here, and I'll try to explain what and why.
Human genetics makes us want to store as much energy as possible in the body, in form of glycogen (glucose storage in muscles and liver) and adipose tissue (fat). The reason for this lies in the fact that up until recently there wasn't plentiful of food available in our surroundings. Because of that, individuals storing energy at moments it was accessible were the ones with a higher survival chance. That is why our bodies evolved in such a way that energy storage was possible.
Today, when hunger is nearly exterminated in well-developed countries, and food is accessible at every step, many still act as if their next meal were their last. People often in the first half of the day ingest the amount of calories enough for the whole day. In that case, any further calorie intake (e.g. consuming an evening meal) would overstep the daily needs and the body would store it safely.
Skipping dinner would be an efficient way to regulate calorie intake in this case, as well as body weight. But does that mean it is necessary and that it is the only way? Of course not.
Who likes going to bed hungry anyway? The way we maintain balance between energy intake and spending energy is less important than actually achieving it.
Before I continue with examples, I'd like to explain the term „storage“.
Using the verb „to store“ is a simple way of explaining weight gain. The mechanism of gaining fat is more than just storage. It's also about changes in oxidation ratios of certain macronutrients. This means that carbohydrates do not turn into fat (except in case of extremely high intakes and/or very low fat intake). So how do we get fat?
Our body uses most of the carbohydrates as well as a smaller portion of fats we ingested as a source of energy. This way the calorie surplus mostly contains fats, which are stored directly into our fat deposits..
Turning carbohydrates into fats is just not rhe best idea for the body because it requires significant amount of energy (ATP).
Another conclusion we can draw from this is that calorie surplus does not relate to a too high intake of a certain macronutrient (protein, carbohydrate, fat) – it doesn't have a singular source. What we can say is that it results in storing fats into adipose tissue.
Going back to the example I promised.
Zdenka has a daily energy need of 2000 kcal and eats three meals per day – breakfast, lunch and dinner.
Zdenka ingests 1000 kcal for breakfast and for dinner, totaling 2000 kcal. This way she completed her daily energy needs before 6 PM. But, due to hunger and habit, at 8 PM she has dinner containing 1000 kcal and this way exceeds her daily needs. Eating past 6 PM makes Zdenka fat.
Zdenka was very busy the entire day and had no time to eat until she came back home at 8 PM. Starving, she ate everything in sight, ingesting 3000 kcal. Easting past 6 PM makes Zdenka fat.
Zdenka was busy again and had no time to eat until she came back home at 8 PM. But she somehow contains herself and doesn't go overboard so she eats dinner of 2000 kcal. Calorie intake equals the daily needs and body weight remains the same. Eating past 6 PM does not make Zdenka fat.
Our heroine had a 500 kcal breakfast, 500 kcal lunch, and a 500 kcal dinner, creating a 500 kcal deficit. Eating past 6 PM makes Zdenka lose weight?!
From these simplified, yet not unreal scenarios, you can see how the timing of the calorie intake is not the most important thing when it comes to regulating weight. I would argue that skipping dinner can even have a negative effect, mostly psychologically, and disturb sleep due to feeling of hunger.
There are no other significant risks. I'd like to single out the situation I mentioned earlier – training at night, especially intense training. Skipping dinner could in this case have a negative effect on recovery process and I do not recommend it.
Skipping dinner, and any other meal, could lead to weight loss if its calorie value is not compensated for in another meal. Those that lost weight this way claim that skipping dinner was key to success, not realizing it was actually the calorie deficit. The body is a flexible machine and the same calorie deficit can be achieved in more than one way. Every person should find the best suitable way – the one you can stick to for the longest – bearing in mind all other nutrititional needs should be accounted for.