Why do I have extreme tiredness after eating?

We’ve all felt that familiar wave of sleepiness after a heavy meal. This is usually a normal response that can often be managed by adjusting what we eat and when. However, in some cases, it could be linked to a medical issue.

What you eat

Certain foods are more likely to make you feel tired after eating than others.

Helena Barham, Nutritional Therapist and Founder of Nourish&Be, London, UK explains that food or drinks that cause a sharp spike in blood sugar will likely be followed by a blood sugar low. This can lead to an energy slump, leaving you feeling tired and sluggish.

Although different foods affect people in various ways, these foods are typically:

• Refined carbohydrates - such as sugary snacks, sweets, cakes, white bread, and pasta.

• Turkey, cheese, eggs, and fish - all contain tryptophan, an amino acid that helps produce serotonin and melatonin, which may cause sleepiness.

• Drinks - such as sugary and alcoholic beverages.

How much you eat

It's not just what you eat, but how much you eat, that can make you feel tired after a meal.

"Eating too much can lead to lethargy - feeling slow and tired - as your body diverts energy to digesting food," says Barham. "But not eating enough can also lead to fatigue, as well as irritation."

When you eat

Regularity is crucial for the circadian rhythm - your body's 24-hour internal clock.

Barham warns that eating too late can disrupt your circadian rhythm, making it harder for you to fall asleep. This may lead to you experiencing tiredness during the daytime.

"Research shows that skipping breakfast and eating meals at irregular times are both related to increased fatigue," she says. "To promote energy, try sticking to the same feeding schedule - for example, eating breakfast between 8-9am."

Digestion

Our bodies work hard to digest food and extract all the necessary nutrients we need from it.

Barham explains that the digestive process requires a significant amount of energy.

"We rarely give credit for the incredible things going on inside us after every meal," she says. "So if we overload our system - for example, eat too much - then this can lead to fatigue as our energy is diverted to tackling the meal."

Blood sugar

Your blood sugar rises after eating, which means this too can affect your energy.

"If your blood sugar levels are kept within a healthy zone, then tiredness should not be an issue," says Barham. "But if your blood sugar spikes - for example after a sugary drink, cake or sweet - then your body responds with a blood sugar crash. This can cause tiredness, irritation, even hunger."

According to Barham, some blood sugar conditions can cause extreme fatigue after eating.

These include:

• Poorly managed diabetes and reactive hypoglycaemia - can both lead to extreme fatigue.

• Insulin resistance (the precursor to diabetes) - can also lead to fatigue as sugar is unable to enter cells and provide energy.

Sleep quality

Poor sleep can cause hormonal imbalances - such as higher cortisol levels and reduced insulin sensitivity.

Barham explains that this may affect how the body processes glucose and lead to fatigue after eating.

"Poor sleep can also increase hunger and decrease willpower," she adds. "This makes you more likely to reach for the easy energy sources of refined carbohydrates, which often trigger a blood sugar spike and subsequent crash."

Barham explains that some sleep disorders and health conditions can cause extreme fatigue after eating.

These include anything that affects your sleep, such as:

• Insomnia.

• Anxiety.

• Obstructive sleep apnoea (OSA).

• Alcoholism.

• Drug use.

Food allergies and intolerances

Allergies, intolerances and sensitivities to certain foods can contribute to post-meal fatigue.

Barham explains that this is because an immune response is triggered by that particular food or component - such as those containing histamine, gluten, or dairy. This response can divert energy from other bodily functions, contributing to fatigue as the body focuses on managing inflammation and detoxification.

Medicines

Beta-blockers, antidepressants, and antihistamines can all cause tiredness, so be sure to check the side effects included on your medicine label.

Barham advises you to keep a diary of when the tiredness occurs.

"Is it always at the same time of day? Is it often after a meal?" she says. "Talk to your doctor or pharmacist about the side effects of medicines and never make any changes without getting medical advice."

Underlying health conditions

While we've already discussed some health conditions that can lead to extreme tiredness after eating, there are other conditions that may contribute as well.

Barham says these can be:

• Crohn’s disease and inflammatory bowel disease (IBD).

• Small intestinal bacterial overgrowth (SIBO).

• Gastroesophageal reflux disease (GERD), or heartburn/reflux.

• Irritable bowel syndrome (IBS).

• Chronic fatigue syndrome (CFS).

• Anaemia.

• Thyroid conditions.

• Adrenal disorders - affect the function of your adrenal glands.

• Long-term stress.

• Various gut disorders.

If you're worried that a health issue may be causing your tiredness, Barham also suggests you keep an eye out for certain symptoms.

"Speak to your doctor to dig deeper into issues that may otherwise go overlooked," she says.

To effectively manage and reduce post-meal tiredness in your daily life, Barham recommends combining the above tips with a healthy diet, stress reduction, and exercising within your limits.

She concludes by suggesting you consider speaking to a nutritional therapist for a more personalised care plan.