Hunger vs thirst: know the difference

You have a gnawing feeling in your stomach, a headache and you’re feeling a little dizzy. You go to the fridge to find something to make you feel better. Do you take a bottle of water or take the last slice of leftover milk tart? Are you thirsty or are you hungry?

The signals our bodies send us when we are hungry are like those of thirst. All too often the two are confused. With food and drinks always being available we tend to eat and drink without feeling hungry or thirsty, and many of us have forgotten how it feels and how to distinguish one from the other.

Hunger vs thirst

What is hunger?

Hunger is the demand for energy. It is a feeling we get when our energy levels are running low and need to be topped up.

What are the signs of hunger?

  • An empty feeling in your stomach
  • Tiredness
  • Feeling light-headed
  • Shakiness
  • Difficulty concentrating
  • Dizziness
  • Headache

What drives hunger?

Our hunger, and therefore need to eat, is influenced by many factors, from within the body and external influences. The hypothalamus in the brain decodes signals that it receives from:

  • Contractions in an empty stomach.
  • The absence of nutrients in the small intestine’
  • Hormones, such as leptin and ghrelin.

If we have not eaten for a while, the signals received by the hypothalamus will tell us that we are hungry and need to eat.

Physiological factors are not the only ones that influence whether we eat. We are often driven to eat, even when we are not hungry. It may be a social situation that requires you to eat, or maybe you derive comfort from eating and will then eat when you feel stressed.

It’s important to recognise what drives you to eat. Are you eating in response to genuine hunger, or are your eating in response to your emotional state?


What is thirst?

Thirst is a conscious sensation of the need to obtain and drink fluids high in water content. It’s a sensation we get when our hydration levels are starting to drop.

What are the signs of thirst?

  • Dry mouth
  • Dry skin
  • Dark-coloured urine
  • Tiredness
  • Feeling light-headed
  • Dizziness
  • Headaches

What drives thirst?

As with hunger, the sensation of thirst is triggered by both internal and external factors. Physiological factors that tell the brain that we need to drink include:

  • Less saliva is being produced
  • Decrease in blood volume
  • Increased concentration of salt

Other factors that drive the thirst mechanism are social, cultural and psychological. We don’t only drink fluids because we are dehydrated, we also drink to be sociable, when we engage in cultural ceremonies and, as with hunger, we may drink because we derive pleasure from drinking.

Can hunger and thirst be confused?

While the main signals for hunger (empty feeling in your stomach) and thirst (a dry mouth) are quite distinct, if you are focusing on something else and ignoring these signals, the signs that come a little later are alike and may result in you eating a toasted sandwich instead of drinking a glass of water.

It’s quite common for someone to think they are hungry when they are actually thirsty. This means that you will go through your day eating often and drinking very little.

Considering that we need to eat just the right amount of food and drink just the right amount of water to remain healthy, consuming food and drinks in such a manner means that we are causing an imbalance in energy, nutrients and water.

When it comes to health, and in particular, weight loss and blood glucose control, it’s important to identify hunger and thirst correctly to prevent overeating or dehydration.

Eating too much has obvious consequences, especially if we choose unhealthy foods. If we habitually eat when we are actually thirsty, there is a good chance that our food intake will be too high resulting in weight gain and raised blood glucose levels.

Water is involved in almost all bodily processes including digestion, the absorption and utilisation of nutrients, elimination of waste and brain function. None of these processes will work at an optimal level if we are in a state of dehydration.

Mild dehydration causes thirst and other symptoms mentioned above, leaving us feeling tired and lethargic. The symptoms worsen as the state of dehydration increases, effecting heart rate, breathing and mental state.

Stop and ask yourself

Next time you are feeling hungry, stop and ask yourself:

  • When last did I have something to eat?
  • What did I eat? Was it enough?
  • When last did I have something to drink?
  • Is it hot today?
  • Have I done any exercise today?

We need to eat every three to six hours to maintain our blood glucose and energy levels. Our meals should be balanced and provide us with the energy and nutrients to make it comfortably to our next meal without having to eat another big meal or snack.

Water is not stored in the body and constantly needs to be replaced. Our water requirements are roughly two litres per day. More if it’s very hot or if you have lost a lot of water through sweating on your morning run.

Unlike eating, it is a good idea to drink consistently throughout the day to avoid dehydration and to keep your energy levels high and your brain sharp.

Tips to drink more water

  1. Keep a bottle of water with you.
  2. Keep a jug of water on your desk.
  3. Add sliced lemon, mint, strawberries or any other fruit or herb to the water to make it more interesting.
  4. Add ice to make it more refreshing.
  5. Try sparkling water to make it more exciting.
  6. Set a goal and set reminders to help you reach your goal.

So, next time you are standing in front of the open fridge, looking for something to make you feel better, reach for the ice-cold water first.  If you are still hungry 15 minutes later, go back for something to eat, but choose a fruit instead of the milk tart!


Wendy Lord is a registered dietitian, based in Sandton. She has been guiding people towards a healthier lifestyle with practical advice and gentle encouragement for more than 20 years. Her main area of interest is conditions of lifestyle including weight loss, diabetes and heart disease. She strives to make her advice family-friendly so that everyone enjoys the same meals.  

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