Food or Physical Activity?

Picking sides in the energy balance equation

As the holidays draw to a close and children start heading back to school its is vital to get yourself and the kids back into the school routine, organising after school sport, switching computer game time with homework time, limiting TV time, and producing quick, easy and healthy family dinners at the table.

With unpleasant stats on childhood obesity and the fact many families are becoming increasingly squeezed for time it’s worth entering the debate on what is more effective – food intake or physical activity?

We know the stats are unpleasant with one in four children overweight or obese in Australia. But with our busy lifestyles and often not enough hours in the day, Dietitian’s are often asked, what is the easiest way to help kids maintain a healthy weight? One of the main causes of obesity is energy imbalance, with epidemiological studies indicating that children’s habitual energy expenditure has declined and their energy intake has increased. However, the underlying cause cannot be related to just one factor. A combination of everything that makes tasty, tempting, energy dense, nutrient-lacking food items easily available, convenient, cheap and marketable is one major contributor, along with every technological advance that results in us doing less physical work; washing machines, dryers, mix masters, cars and the endless list continues all which makes us more prone to excessive energy intake and inadequate physical activity than any previous generation.

The science suggests that there is little evidence dietary composition or macronutrient distribution has a meaningful influence on weight management independent of energy intake. However, it has been established that diet can affect satiety and is likely to influence weight indirectly by affecting the quantity of kilojoules eaten.

A recent review of the research completed in the US set out to understand the relative importance of overconsumption and physical inactivity to excess weight gain. The researchers found that there is wide variation in data quality and in the accuracy of measures of energy intake, and based on the available evidence there was no consensus on whether overconsumption or physical inactivity was the main driver for weight gain among US children and teens.

Despite this conclusion, intervention studies usually report that dietary modifications can be effective at weight loss on their own, whereas exercise based interventions do not, although a combination of the two works better than either on its own. From a practical perspective it is important to think about the most efficient ways to lose weight, and whilst we always, and will continue to recommend physical activity which has powerful influences on weight and health, we have to accept the challenge of getting an increasingly sedentary generation to participate in physical activity, all which could be undone by an unhealthy food or drink choice.

If you think about the 1000kJ a child might burn during 1 hour of bike riding per day and then consider the 2500kJ++ in a Happy Meal that takes less than 5 mins to eat, it’s easy to understand how hard it is becoming to maintain a healthy weight. This example emphasises the challenge we will continue to face unless we improve the quantity and quality of children’s diets. A study just published has found that that detailed representation of fast food and soft drink brands (developed via experience and advertising) has higher scores on an ‘added flavour’ sugar/fat/salt liking palate, fundamentally changing children’s taste palates to increase their liking of highly processed and less nutritious foods. The researchers concluded early food-related behaviours are important and if we want to intervene we need to start when children are young.

Back to school lunch box tips

  • Pat wet ingredients dry with a paper towel and layer lettuce between wet ingredients and bread to prevent moisture from spreading. Prepare sandwiches as close to lunchtime as possible to ensure freshness.
  • Older students might go for something a little more gourmet. Tempt teen tastebuds with roast vegies on Turkish bread or a wholemeal wrap.
  • If the kids keep throwing out their crusts, beat them to it. Try using breads with no crust, such as wraps or Turkish bread. Alternatively, cut the crust of regular bread and use the left over crusts to make croutons or breadcrumbs.
  • Wholegrain dinner rolls with healthy fillings can be used instead of larger bread rolls for younger kids. Cutting sliced bread into different shapes or creating a face by adding a grape cut in half for the eyes, a piece of carrot for the nose and a capsicum mouth can make lunches fun.
  • Get kids involved with a best filling competition or a naming competition for sandwiches. Encourage the school canteen to have a reduced price or a meal deal with a free apple or yoghurt.
  • Introduce wholegrain breads into the kids’ diet with ‘zebra’ sandwiches by using one slice of wholegrain and one white slice. Wholegrain crispbreads and rice cakes are a good alternative for kids who don’t like bread.


Katz DL. Unfattening our children: Forks over feet. International Journal of Obesity (2011) 35, 33-37.
Bleich SN et al. Relative contribution of energy intake and energy expenditure to childhood obesity: a review of the literature and directions for future research. International Journal of Obesity (2011) 35, 1-15.
Cornwell TB et al. Alternative thinking about starting points of obesity. Development of child taste preferences. Appetite (2011) Published online ahead of print.


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