When to Eat?

Summarized by Robert W. Griffith, MD
March 11, 2005

Introduction

People often ask "Is it better to eat many small meals at random times during the day, or to have regular meals"? Of course, the answer depends a bit on what's meant by "better". Let's assume that we're looking for better health and better weight control. Scientists have been trying to compare the apparent benefits of nibbling and gorging for years, but haven't really reached any firm conclusions. But today we're a step nearer, thanks to a study reported in the American Journal of Clinical Nutrition.

Scientists from Nottingham, UK, investigated whether taking regular or irregular meals affected energy intake, energy expenditure, blood insulin levels, blood glucose, and blood lipid profiles in 10 healthy but obese women.

What was done

The women had an average body mass index (BMI) of 37 - values over 30 are considered 'obese'. Half of them ate irregularly for two weeks, followed by two weeks with regular meals, while the other half carried out the same two phases, but in reverse order. (This is known as a 'cross-over' experimental design.)

In the 'regular' phase, the women were asked to consume their usual diet on 6 occasions throughout the day. In the irregular phase, they were asked to eat the same amount and type of food, but in a chaotic fashion; on day one they had 7 meals, day two 4 meals, and thereafter 9, 3, 5, 8, 6, 5, 9, 8, 3, 4, 7, and 6 meals on days 2-14 of the phase, respectively.

A standardized test meal was given at the beginning and end of each phase to allow measurement of changes that would show any effect of regular vs. irregular meals. Blood glucose, blood lipids, and insulin levels were measured before and for 3 hours after the test meal.

The subjects kept food intake records, so that energy intake could be calculated, and the utilization of the energy consumed determined.

What was found

The regular eating regime was found to result in lower energy intake, i.e. the women ate fewer calories during this phase. Irregular eating, on the other hand, resulted in lower energy-utilization (in the form of body-warming) for a given amount of calories. This suggested that irregular eating may reduce insulin sensitivity, which is associated with an increase in the risk of developing type 2 diabetes.

Regular eating was also linked with lower total cholesterol and LDL-cholesterol levels. Moreover, the peak insulin levels after the test meal were lower after the regular-eating than after the irregular-eating phase.

There were no other significant differences between the results after the two phases.

What these results mean

The findings show that regular eating habits are more beneficial to your health than irregular (or chaotic) eating habits - all other things being equal. Apart from the blood lipid changes, the irregular-eating reduction in energy utilization may be responsible for decreased satiety (feeling of fullness) and therefore an overall increase in appetite.

An accompanying editorial in the same journal points the way to further important studies that need to be done in this area.¹ What are the benefits of a larger breakfast and a smaller evening meal on weight gain, for instance? We clearly need a better understanding of the importance of timing of eating as a method to optimize energy intake and utilization - in other words, to keep to a healthy weight. In the meantime, eat regular meals regularly!

Source

• Beneficial metabolic effects of regular meal frequency on dietary thermogenesis, insulin sensitivity, and fasting lipid profiles in healthy obese women. HR. Farshchi, MA. Taylor, IA. Macdonald,  et al., Am J Clin Nutr, 2005, vol. 81, pp. 16--24

Footnotes
1. When to eat and how often? EJ. Parks, MA. McCrory, Editorial. Amer J Clin Nutr, 2005, vol. 81, pp. 3--4

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