Think carefully when preparing a lunchbox for school children.

The number of South African children who are overweight or obesity is on the increase.

Professor Salome Kruger of the Nutrition Centre of Excellence at the University of North West believes work needs to be done to combat this problem in school-going children.

She is calling on parents to jump in and help, by preparing healthy school lunch boxes for their children and to be aware of the importance of making good choices.

According to Kruger, physical activity should be made part of the school curriculum, and extra fun sport activities should be organised for children who do not make the team.

She said more nutrition information in the school curriculum could also add value.

Have a healthy mix of options in a lunchbox. Pexels

Kruger said one of the main problems lay with school tuck-shops and vendors sitting at the school gates with their unhealthy offerings.

"Tuck-shops often sell fizzy cold drinks, sweets, biscuits and crisps. These are high in either sugars, refined starch or salt and fat," she said.

"They are sources of energy, but in our context of under nutrition when it comes to vitamins and minerals, such as iron, these foods do not make a contribution to feed a growing child."

Vendors at school gates sell similar foods, although they sometimes offer healthier alternatives such as chicken feet, fresh fruit or sandwiches.

"Efforts should be made to sell milk, milk drinks, yogurt, maas and fresh fruit in tuck-shops," she said.

According to Kruger, children need to eat more frequently than adults, due to their smaller gastric capacity and relatively greater need for nutrients such as iron and calcium in foods to sustain growth.

"It is necessary to focus on nutrients for growth and development, such as protein, calcium, iron and zinc and vitamins for immune function," said Kruger.

Prepare protein foods for lunch boxes

These would include eggs, cheese, nuts, peanut butter, biltong and cold meats, salads with beans or lentils. Milk (fresh or flavoured) and yogurt are also good sources of protein, calcium and B-vitamins.

"Eating fresh vegetables and fruits instead of drinking fruit juice leads to greater satiety, generally combined with a lower sugar intake," Kruger said.

She explained that whole-wheat bread and crackers for sandwiches could be alternated with muffins or oat cookies as a source of energy and B-vitamins.

Balanced diets contain whole foods, such as proteins (meat, eggs, legumes, milk), fruits and vegetables, whole-grain starchy foods and small amounts of added fats and oils plus water.

Whole fruits contain fibre, making it necessary for them to be chewed before swallowing. Chewing causes the fruit to be absorbed over a longer time than juice does, and sends a message to the brain that food has been eaten and there is now a feeling of fullness