Why Is Healthy Eating So Hard? Science Behind Craving Sugar & Carbs

We all want to eat healthily, especially as we reset our health goals at the start of a new year. But sometimes these plans are sabotaged by powerful cravings for sweet, salty or carb-heavy foods. So why do you crave these foods when you’re trying to improve your diet or lose weight? And what can you do about it?

There are many reasons for craving specific foods, but let’s focus on four common ones:

1. Blood sugar crashes

Sugar is a key energy source for all animals, and its taste is one of the most basic sensory experiences. Even without specific sweet taste receptors on the tongue, a strong preference for sugar can develop, indicating a mechanism beyond taste alone.

Neurons responding to sugar are activated when sugar is delivered to the gut. This can increase appetite and make you want to consume more. Giving into cravings also drives an appetite for more sugar.

In the long term, research suggests a high-sugar diet can affect mood, digestion and inflammation in the gut.

While there’s a lot of variation between individuals, regularly eating sugary and high-carb foods can lead to rapid spikes and crashes in blood sugar levels. When your blood sugar drops, your body can respond by craving quick sources of energy, often in the form of sugar and carbs because these deliver the fastest, most easily accessible form of energy.

2. Drops in dopamine and serotonin

Certain neurotransmitters, such as dopamine, are involved in the reward and pleasure centres of the brain. Eating sugary and carb-rich foods can trigger the release of dopamine, creating a pleasurable experience and reinforcing the craving.

Serotonin, the feel-good hormone, suppresses appetite. Natural changes in serotonin can influence daily fluctuations in mood, energy levels and attention. It’s also associated with eating more carb-rich snacks in the afternoon.

Low carb diets may reduce serotonin and lower mood. However, a recent systematic review suggests little association between these diets and risk for anxiety and depression.

Compared to men, women tend to crave more carb rich foods. Feeling irritable, tired, depressed or experiencing carb cravings are part of premenstrual symptoms and could be linked to reduced serotonin levels.

3. Loss of fluids and drops in blood sugar and salt

Sometimes our bodies crave the things they’re missing, such as hydration or even salt. A low-carb diet, for example, depletes insulin levels, decreasing sodium and water retention.

Very low-carb diets, like ketogenic diets, induce “ketosis”, a metabolic state where the body switches to using fat as its primary energy source, moving away from the usual dependence on carbohydrates.

Ketosis is often associated with increased urine production, further contributing to potential fluid loss, electrolyte imbalances and salt cravings.

4. High levels of stress or emotional turmoil

Stress, boredom and emotional turmoil can lead to cravings for comfort foods. This is because stress-related hormones can impact our appetite, satiety (feeling full) and food preferences.

The stress hormone cortisol, in particular, can drive cravings for sweet comfort foods.

A 2001 study of 59 premenopausal women subjected to stress revealed that the stress led to higher calorie consumption.

A more recent study found chronic stress, when paired with high-calorie diet, increases food intake and a preference for sweet foods. This shows the importance of a healthy diet during stress to prevent weight gain.

What can you do about cravings?

Here are four tips to curb cravings:

1) don’t cut out whole food groups. Aim for a well-balanced diet and make sure you include:

• sufficient protein in your meals to help you feel full and reduce the urge to snack on sugary and carb-rich foods. Older adults should aim for 20–40g protein per meal with a particular focus on breakfast and lunch and an overall daily protein intake of at least 0.8g per kg of body weight for muscle health
  
  
• fibre-rich foods, such as vegetables and whole grains. These make you feel full and stabilise your blood sugar levels. Examples include broccoli, quinoa, brown rice, oats, beans, lentils and bran cereals. Substitute refined carbs high in sugar like processed snack bars, soft drink or baked goods for more complex ones like whole grain bread or wholewheat muffins, or nut and seed bars or energy bites made with chia seeds and oats

2) manage your stress levels. Practise stress-reduction techniques like meditation, deep breathing, or yoga to manage emotional triggers for cravings. Practising mindful eating, by eating slowly and tuning into bodily sensations, can also reduce daily calorie intake and curb cravings and stress-driven eating

3) get enough sleep. Aim for seven to eight hours of quality sleep per night, with a minimum of seven hours. Lack of sleep can disrupt hormones that regulate hunger and cravings

4) control your portions. If you decide to indulge in a treat, control your portion size to avoid overindulging.

Overcoming cravings for sugar, salt and carbs when trying to eat healthily or lose weight is undoubtedly a formidable challenge. Remember, it’s a journey, and setbacks may occur. Be patient with yourself – your success is not defined by occasional cravings but by your ability to manage and overcome them.

This article by Hayley O'Neill, Assistant Professor, Faculty of Health Sciences and Medicine, Bond University was published in The Conversation.