Why is 8,700 kilojoules (kJ) (or 2000 calories) used as a benchmark figure for daily food intake?

The figure of 8,700kJ comes from national surveys of what Australians supposedly eat. According to Food Standards Australia New Zealand, we eat, on average, around 8,700 kJ a day. This figure is widely used as a benchmark as the basis of food labels such as the Percent Daily Intake (%DI) values. The Daily Intake Guide or %DI is a set of reference values for an acceptable intake of nutrients including:

  • Energy
  • Protein
  • Fat
  • Saturated fat
  • Carbohydrate
  • Sodium (salt)
  • Sugars
  • Dietary fibre

It’s important to note that 8,700 kJ a day is an average. The actual number of kilojoules you require will vary depending on your age, gender, life stage (if you’re growing or are pregnant as this requires more energy), weight, height, disease state, how physically active you are and what type of activity you engage in.

8,700kJ of pizza vs 8,700kJ of whole foods look very different — are all calories made equal? 

Firstly, not all calories are created equal. This is a very common misconception – that a calorie from fruit is the same as a calorie in pizza. This may be true when they’re on the plate since all “calories” have the same amount of energy. However, the calories on paper are not necessarily the calories we actually receive due to the human body being a highly complex biochemical system with elaborate processes that regulate energy balance. Furthermore, the calories in fat, protein and carbohydrates (nutrients) have a different biological influence on satiety, metabolic rate, brain activity, blood sugar and the way our body stores fat.

Secondly, unhealthy food is unhealthy food, no matter how many calories it has. Calories from nutrient-dense foods versus nutritionally-poor foods (e.g. processed or refined carbs) will have different effects on the body. Healthy, nutrient-dense foods will keep hunger at bay, help maintain stable blood glucose levels, reduce cravings, and allow your brain to signal to your stomach that it’s full. Nutrient-poor foods will have the opposite effect, causing hormonal dysfunction, spiking insulin levels, increasing cravings, suppressing satiety signals and encouraging overeating.

Why is it important to eat enough food, but not to overeat?

To put it simply, it’s important to eat enough food so you are meeting your recommended dietary intake of nutrients to sustain good health. If you are not consuming enough calories or lack variety in your diet, you will be at risk of malnutrition and possible nutrient deficiencies. This may then lead to, additional acute and chronic health problems such as hormonal imbalances, fertility issues, developmental problems in infants and children and mental health problems to name a few. Additionally, food gives us energy to function, and perform daily activities and tasks to the best of our ability. Too little energy (from food) can result in tiredness and fatigue, poor concentration, poor memory, food craving and even weakness.

Overeating, however, can lead to, other short-term and long-term health problems. Short-term effects of overeating include gastrointestinal issues such as bloating and gas, lethargy and weight gain. Long-term effects can be more serious. The unhealthy weight gain that results from overeating can result in overweight and obesity, which is associated with increased risk of chronic health issues such as coronary heart disease, type 2 diabetes, stroke, high blood pressure, sleep apnoea and cancer. Additionally, any self-esteem issues linked to being overweight or obese, can cause a myriad of mental health problems such as anxiety and/or depression.

What does 8,700kJ look like in one day? 

A “healthy” day may look like the following:

BREAKFAST

  • ½ cup muesli
  • 3 Tablespoons Natural or Greek yoghurt
  • ¾ cup fresh mixed berries
  • Sprinkle of cinnamon

SNACK

Regular skim latte

LUNCH

A large salad consisting of:

  • 1 cup salad greens
  • 1 x 90g tin tuna (drained)
  • 1 tablespoon balsamic, lemon juice and olive oil dressing
  • ¼ small avocado
  • A small handful of cherry tomatoes
  • ¼ cup capsicum
  • 1 teaspoon pumpkin seeds

SNACK

  • 1 apple
  • 10 walnuts

DINNER

  • 160g chicken breast (cooked)
  • ½ cup steamed broccoli
  • ½ cup steamed beans
  • 1 small carrot
  • ½ cup green peas
  • ½ cup quinoa (cooked)
  • 1 Tablespoon olive oil
  • 1 glass wine

AFTER DINNER

  • 2 x squares dark chocolate

 

A “less healthy” day may look like this:

BREAKFAST

  • 2 slices Turkish bread (toast) with butter and Vegemite
  • Large full cream cappuccino

SNACK

  • 1 slice banana bread (from a café)

LUNCH

  • Large beef burger (with tomato, lettuce, cheese and sauce)
  • Large fries
  • 600mL bottle coke

SNACK

  • 1 mug of tea with full cream milk

DINNER

  • Nothing! You’ve used up your total daily intake of 8,700kJ.