Friday May 8 2015
The study involved only 15 women
"Eating little and often – like Jennifer Aniston – could help dieters achieve a healthy weight loss," reports the Mirror. Meanwhile, the Mail Online urges us to "Forget three square meals a day – eating six smaller portions is better for your waistline".
But don't rush to change how often you eat: the claims are based on a tiny study that has been overstated and misinterpreted by the media. In fact, women lost a similar amount of weight regardless of the number of daily meals they ate.
In the study, 11 obese women ate the same low number of calories in either two meals or six meals a day. They lost around the same amount of weight with both diets.
They did retain their non-fat mass (the weight of the body in muscle, organs and bone) better when they were on six meals a day, but the authors warn against drawing firm conclusions from this.
The two-meal pattern seemed to improve levels of "good" cholesterol more than the six-meal pattern. Whether either of these differences would lead to any health benefits for the women was not assessed.
Overall, this study is too small to prove whether six or two meals a day is better for dieters. What is important is to choose an approach to weight loss or healthy weight maintenance that works for you that you can stick to.
Where did the story come from?
The study was carried out by researchers from California State University and other research centres in the US. It was funded by the University of New Mexico.
Nutrisystem Inc, a commercial weight loss company that provides home delivery of calorie-controlled food portions for weight loss, donated all food products used in the study.
The study was published in the peer-reviewed medical journal, Nutrition Research.
The Mirror and the Mail Online have very similar coverage, suggesting that the stories may be based on the same press release. They both say that, "Those who ate six meals a day had healthier levels of glucose, insulin and cholesterol". But this is not true.
When the women ate two meals a day, they had better levels of "good" cholesterol than when they ate six meals a day. The levels of other blood fats, glucose and insulin were generally very similar between the groups, and any slight differences were not large enough to rule out having occurred by chance.
What kind of research was this?
This was a crossover randomised controlled trial assessing whether splitting calories into two or six meals had different effects on body composition and blood markers of health.
In crossover trials, the same group of people received both of the interventions being compared in a random order.
This approach is suitable if the effects of the interventions are not long lasting; therefore, it is likely to be a better way to look at short-term effects on blood markers than the long-term effect on weight loss.
What did the research involve?
The researchers recruited 15 adult women who were obese but not diabetic. They randomly assigned them to eat a reduced-calorie diet as either two or six meals a day over two weeks. They then had a two-week break before switching to the other meal pattern.
The researchers measured various blood markers and the women's body compositions during the different parts of the study.
In each part of the study, the food products were the same and delivered to participants in pre-packaged portions. The meals gave about 1,200 calories per day.
During the break, the participants ate four times a day (three meals and a snack). Fluid consumption was not strictly controlled during the trial.
What were the basic results?
Eleven women (73%) completed the study, and four withdrew because they did not comply with the diet, time constraints, or had family issues.
Overall, the women lost weight during the study and reduced their body mass index (BMI), waist circumference, fat mass and percentage of body fat. Their calorie intake reduced from an average of 2,207 calories a day to 1,200 calories.
Women lost similar amounts of weight after the two meals a day period (2.7% loss) and the six meals a day period (2.0% loss). When the women ate two meals a day, they lost more fat-free mass (3.3% loss) than when they ate six meals a day (1.2% gain).
The researchers did not find any difference between fat mass loss, resting metabolic rate, or the levels of insulin, glucose or most fats in the blood when the women were on the different meal frequencies.
"Good" cholesterol (HDL, or high-density lipoprotein) levels increased more when the women were eating two meals a day (1.3% increase) than when they were eating six meals a day (0.12% increase).
How did the researchers interpret the results?
The researchers concluded that calorie restriction was an effective way of losing weight.
Consuming these calories in two meals a day was associated with improved "good" cholesterol levels.
Conversely, consuming the calories in six meals a day preserved fat-free mass during weight loss. Whether either of these changes would have a beneficial impact on health is unclear.
This small crossover trial found little difference between eating the same low number of calories over six meals a day as opposed to two meals a day.
Both patterns resulted in similar weight loss, but the six meal a day group lost less non-fat weight from their bodies, suggesting that they may have, for example, lost less muscle.
However, the authors themselves suggest their body composition findings should be interpreted with care. They did not impose strict fluid replacement rules, and the method they used for measuring body composition could have been affected by how hydrated the women were during the trial.
This was also a very small study (15 obese women), and almost a quarter dropped out before the study finished. The study size may have limited its ability to identify important differences between the groups.
The study was also very short, with each meal frequency tested over a fortnight. The results may not be representative of what would be seen in more diverse groups of people, over a longer period of time, or what would happen if people had to prepare their own meals.
While the news has suggested the findings show that six meals a day is "better", it is not possible to clearly say this from the results. It is unclear whether the difference in body composition seen is reliable and would have any effect on health.
The only other difference was that women had increased levels of "good" cholesterol during the two meal a day period. While this seems to favour the two-meal pattern, whether this difference would be maintained or have a beneficial impact on health is not clear.
Overall, very little can be concluded from this study. What we can say is that obese women eating a calorie-controlled diet can lose weight, and how they split these calories up does not seem to have much impact on their weight loss in the short term.
Some of the participants reported being more "comfortable" with the two meals a day pattern, while others reported the opposite. Reaching and maintaining a healthy weight brings health benefits, and people should use whatever meal frequency they find helps them achieve this.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.