Why do I have less strength after eating than before?

Eating food is a constant and integral part of every person’s life. Eating is a bit like filling up your car. It is supposed to provide energy for our body to work efficiently. But what if we fill the tank to full and still feel like we’re driving with a small car?

Food and nourishment?

The consumption process should be aimed at nourishing the body, not just satisfying physiological hunger. Therefore, when choosing food, we should ensure that we provide the micro and macro elements necessary for the proper functioning of the body. The nutritional status of the body and the availability of nutrients play a key role in the process of energy production in the human body. A common nutritional mistake is to pay attention only to the energy value of products.

Meanwhile, the human body is a very complex system. Many elements are needed for optimal energy production. Proper nutrition is crucial, especially for an athlete. Helps optimize performance during training and competition.

We eat to have energy. Why do I have less strength after eating than before?

As a dietitian, I often hear from clients that after eating a meal (usually a large one) they feel lethargic, without strength and energy. How is this possible when they ate well? Then the question arises: Why do I have less strength after eating than before? Instead of bursting with energy, I feel lethargic.

Some people may additionally experience anxiety, malaise, or even irritation or aggression. It is then typical that after a meal we feel the need to go to bed or eat something sweet. We also often reach for stimulants such as coffee and energy drinks.

Chronic postprandial drowsiness is not normal. It should not occur after eating a meal. With enough sleep and rest, we should have consistent energy levels throughout the day. The most common reason for feeling sleepy after a meal is an improperly balanced diet and too high a meal’s glycemic load (GI). This is related to the level of glucose in the blood.

The glycemic index (GI) is a measure of the ability of carbohydrates in foods to increase blood glucose levels. Consuming a meal with a high GI leads to glycemic disturbances and a large increase in blood glucose. This, in turn, stimulates the pancreas to produce insulin, which is responsible for providing energy to cells. Therefore, eating a large, usually carbohydrate-rich meal leads to a sudden spike in sugar levels in the body. This causes a large release of insulin, which rapidly lowers glucose levels.

Then, due to a drop in blood sugar, we feel a lack of energy drowsiness, and the need to eat another, usually sweet, meal. We may experience similar symptoms of lack of energy and drowsiness when there is too long a break between meals or when the blood glucose level drops due to too low food supply.

How to prevent postprandial drowsiness?

Why do I have less strength after eating than before? As already mentioned, the most common cause of the above-described system of action is too high a glycemic load of meals, as well as an incorrect ratio of carbohydrates to the remaining macronutrients: protein and fat.

The public believes that carbohydrates are the only source of energy for the body. Advertising slogans of the food industry assure us that after confectionery products we will be a volcano of energy. As a result, we often consume too many simple sugars, which disturb glycemia.

Moreover, many runners (especially beginners) overestimate their energy expenditure during training. As a result, they eat more than they need. Yes, physical exercise creates a greater demand for energy and the fact is that runners can afford more than the inactive group of the population. However, it should be remembered that regular running does not mean that we can eat sweets with impunity. Excess sugar in the diet leads to energy overload, unstable glucose levels in the bloodstream, and sudden drops in energy.


Why do I have less strength after eating than before? Furthermore, it has been shown that the feeling of low energy after a meal (fatigue) may be associated with increased levels of circulating inflammatory markers (pro-inflammatory cytokines). A higher level of fatigue after a meal was observed in obese people than in the group with normal body weight.

This is due to the fact that increased adipose tissue content increases the development of systemic inflammation. Additionally, this condition is promoted by pro-inflammatory factors from the diet. Such as an inappropriate ratio of omega-6 to omega-3 acids and too high a share of simple sugars and trans fats, which are abundant in processed foods.

Why do I have less strength after eating than before? How to prevent it?

The first step should be to estimate your daily energy needs to maintain energy balance. For this purpose, we should analyze how much energy we expend during training and how much during everyday activity (depending on the nature of work and the degree of non-training activity). This is where sports watches with built-in heart rate measurements come in handy. Remember that athletes have different needs for carbohydrates. It depends on the type, intensity, duration of training, as well as lifestyle.

Why do I have less strength after eating than before? Another important issue is ensuring the proper balance of meals and the distribution of macroelements. To avoid post-prandial drowsiness, we should ensure the appropriate glycemic load of the foods we eat. Too high a proportion of carbohydrates in relation to fats and/or proteins will disturb the body’s glycemia and cause a feeling of tiredness and drowsiness after a meal. Interestingly, it has been shown that the order in which individual macro elements of a dish are consumed affects the level of postprandial glycemia. It is recommended that protein and fat be consumed first and carbohydrates second. So if your plate includes cooked rice, chicken, and salad with olive oil, it is better to eat the meat or salad first, and then the rice.

Just as a meal containing simple sugars with a high glycemic load is recommended immediately after intense exercise, this is not necessarily the case during the day and during normal functioning.

Remember that not all carbohydrates are created equal. There is a huge difference between eating oatmeal or a banana and eating sweets or ice cream. Carbohydrate products such as whole grains, fruits, vegetables, and legumes are nutritious and valuable products. They are rich in antioxidants, fiber, vitamins and minerals. While processed sugars only provide energy and if consumed in excess, they can be very harmful to health.

What should I do if I feel excessively sleepy after a meal?

If postprandial drowsiness occurs occasionally, there is most likely no reason to worry. It happens to everyone from time to time. However, if you have been feeling excessively sleepy after a meal for a long time and this condition interferes with your daily functioning, you should undergo tests and check how your body’s carbohydrate metabolism functions. This is a condition that should not be underestimated because if neglected it can lead to the development of insulin resistance and then diabetes.

Fasting glucose and insulin tests are used to assess the functioning of carbohydrate metabolism.

Then you should consult the results with your doctor and tell about your symptoms. Then, the doctor may additionally refer us to a blood sugar curve test (oral glucose tolerance test). During the test, fasting insulin and glucose levels are checked, 1 hour and 2 hours after the load.

Currently, the test is performed only on the basis of a referral from a doctor. A clear contraindication to this test is a high fasting glucose level. Then, performing a test with a significant amount of simple sugars may result in serious health consequences.


The standard in the treatment and prevention of postprandial drowsiness is to change the current diet. Appropriate composition and glycemic balance of meals in the diet. The diet should also be highly nutritious. Meet the need for protein, fats, carbohydrates, as well as micro and macro elements. For help, you should seek advice from a dietitian who will help you identify and eliminate dietary errors.


Why do I have less strength after eating than before? The problem of postprandial sleepiness seems to be an increasing social problem and affects more and more people. As a dietician, I also observe them among active people, including runners. Dietary errors are responsible for this condition. Chronic lack of strength after a meal is a phenomenon that should not be underestimated because it can lead to serious health problems.


1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5753973/

2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6001918/

3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5525124/

4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6028526/

5. https://pubmed.ncbi.nlm.nih.gov/17375403/

6. Großkopf, A., & Simm, A. (2020). Carbohydrates in nutrition: friend or foe?. Journal of Gerontology and Geriatrics, 53(4), 290-294: https://pubmed.ncbi.nlm.nih.gov/32333094/

7. Dąbrowska-Górska, B. Reactive hypoglycemia – what is it? Symptoms, diagnosis and diet: https://barbaradabrowska.pl/hipoglikemia-reaktywna-co-to-jest-objawy-diagnostyka-i-dieta/

8. Kobierzycka, K. Emotional changes after eating sugar, part II.

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