It is becoming clear that the traditional advice to reduce energy intake or increase energy expenditure is not able to produce long-term weight loss in many individuals. Recent research suggests that obesity is caused by a combination of metabolic imbalance that leads to insulin resistance as well as a number of subtle lifestyle factors that contribute to slow and steady body fat accumulation. For example research suggests that macronutrient composition plays a part in weight gain, with higher protein diets showing beneficial effects on body weight and body mass index. Meal frequency and regularity have also been shown to influence weight gain. Eating larger meals earlier in the day has been shown to increase satiety and regularly spaced meals have been shown to decrease energy intake. Evidence is therefore accumulating that the method of food ingestion can be just as an important factor as food selection.
For example, researchers1 investigated the effects of bite size and oral processing time on the satiation of healthy subjects exposed to ad libitum food intake. In a randomised cross-over designed study, the subjects were fed a custard mixture that consisted of milk, whey protein, thickening agents, cocoa, colouring agents, salt and aroma, which contained 395 kJ (94 kcal), which included 2.3 grams protein, 14.7 grams carbohydrate and 2.8 grams of fat. A machine dispensed small (5 gram), large (15 gram) or unrestricted bite sizes into the mouths of the subjects, upon which they were instructed to chew for a fixed length of time. Chewing time was either free (in combination with unrestricted bite size) or fixed to 3 or 9 seconds. The researchers used sound signals to indicate the oral processing time to the subjects and the subjects were allowed to continue consumption until they felt satiated.
The results showed that the subjects consumed more food when the bite sizes were larger, compared to when they were small. In addition, when oral processing time was increased food intake was reduced. Subjects consuming food with small (5 gram) bite sizes had mean intakes of 382 grams and 313 grams for the 3 and 9 second oral processing time, respectively. Subjects consuming the food with large (15 gram) bite sizes had mean intakes of 476 grams and 432 grams for the 3 and 9 second oral processing time respectively. Mean food intakes under the unrestricted bite size conditions were 462 and 455 grams, respectively. Taken together these results support previous studies that have shown that the methodology surrounding ingestion of food can have a significant effect on satiety and food intake. Large bite size and short oral processing time might be associated with a busy lifestyle and short meal time.
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