Nov. 3, 2003 -- Eat the wrong kind of breakfast cereal, and you'll be hungrier and eat more at lunchtime, a new study shows. It's one more inside clue to the weight loss mystery -- and another reminder that in excess simple carbs may not be good for us.
A new study provides evidence favoring foods with low-glycemic indexes (GI) such as whole-grain breakfast cereals including oatmeal, bran cereal, and muesli (a Swiss tradition). It shows that foods with low GI's can keep us feeling full and that these foods may have an important role in weight loss and obesity management.
The key is what researchers call glycemic index -- a measure of the effect of foods on blood sugars. Studies have shown that whole grains and other foods with low GI's can help keep blood sugar levels in normal ranges and help people maintain a feeling of fullness.
Foods with low GI's can keep our hunger in check. It helps people lose weight -- they simply eat less, writes Janet M. Warren, PhD, a nutrition and food science writer with Oxford Brookes University in England. Her study is published in this month's Pediatrics.
Rice Krispies vs. All-Bran
To test this theory, Warren and her colleagues tried three types of breakfasts on a group of students attending a middle school in Oxford. They monitored how satisfied the children felt after breakfast and how much each child ate at lunch.
Her study involved 37 boys and girls; 30% of the children were overweight.
The children were divided into five groups. Every week, each group randomly received one of three test breakfasts for three consecutive days, in addition to fruit juice.
- Breakfast 1: Whole-grain breakfast cereal such as All-Bran, muesli, porridge, or whole-grain bread (a low-glycemic index breakfast).
- Breakfast 2: Whole-grain breakfast cereal or bread, plus sugar for additional taste (a modified low-glycemic index breakfast).
- Breakfast 3: Refined-wheat cereals like Corn Flakes, Coco-Pops, Rice Krispies, or white bread (a high-glycemic index breakfast).
After breakfast, each child was asked whether they felt full -- and if they liked the way the breakfast tasted. They were instructed not to eat or drink anything until lunchtime, except water and a small serving of fruit -- an apple, grapes, or an orange. Since the school did not have a shop or vending machine, it wasn't a problem, Collins writes.
Lunch was a buffet-style meal, and children were allowed free range to all sorts of sandwiches -- ham, chicken, egg, peanut butter, plus salad, cheese sticks, bread sticks, potato chips, cookies, cake, yogurt, cottage cheese, water, and fruit-flavored drinks.
A researcher was on site, keeping track of how much food each child took and how much each ate -- without the kids knowing it.
Thumbs Down: Rice Krispies, Corn Flakes, etc.
All the children reported being full after breakfast, but they liked the sugary breakfast cereal best, followed by the whole-grain-plus-sugar breakfast. The whole-grain breakfast came up last in likeability.
However, hunger ratings before lunch -- and amount eaten at lunch -- were a different matter. The Breakfast 3 group, those who eat a high-glycemic index breakfast, were hungrier and ate far more than the other groups. This was true whether the child was overweight or not, boy or girl.
In fact, children in Breakfast 1 and 2 groups ate less at lunch than the children who eat a high GI Breakfast -- the junk-breakfast cereal group.
The addition of sugar did not have any big effect on the glycemic index of the whole-grain breakfast, authors note. However, bland cereals such as oatmeal and porridge are more palatable with a small bit of sugar -- and could keep more kids eating it, they say.
It's another lesson that simple carbohydrates -- whether in the form of sugar or foods made with refined flour-- can short circuit the best intended weight loss efforts.
SOURCE: Warren, J. Pediatrics, Nov. 2003; vol 112: pp 414-419.