When you eat more important than what you eat, claims study

It’s a question that obesity experts have long puzzled over: Can when you eat affect your ability to lose weight?

A new study conducted in Spain is claiming that those who eat their main meal earlier in the day will have an easier time dropping pounds than those who eat a big meal later on, reports the Toronto Star.

“Eating late may influence success of weight-loss therapy," write the researchers. "Novel theraputic strategies should incorporate not only caloric intake and macronutrient distribution — as is classically done — but also the timing of the food.”

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However, as is often the case in the medical community, not everyone is an agreement.

“The conclusion of this study is a bit of a leap,” says Rena Mendelson, a professor of nutrition at Ryerson University. “I don’t think it’s a very strong paper."

She says the idea that the timing of food intake can affect weight loss is only a theory at this point.

The study, Timing of Food Intake Predicts Weight Loss Effectiveness, was conducted by Spanish and American researchers at Spain’s University of Murcia, Tufts University in Medford, Massachusetts and Boston’s Brigham and Women’s Hospital.

Researchers monitored the diets of 420 overweight Spaniards over a 20-week weight-loss treatment. They divided subjects into two groups: those who ate their main meal of the day before 3 p.m., and those who ate it after 3 p.m. They controlled a wide range of other variables, including energy intake and expenditure, appetite hormones and sleep duration. They also looked for something called a CLOCK genotype, a specific gene that has been associated with obesity in previous research.

As the experiment progressed past the five-week point, the later eaters began to display a slower weight-loss rate, and ultimately lost less weight than the early eaters.

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While the results of the study may sound convincing, Mendelson points out that there are several confounding variables that make it difficult to say whether it was specifically the meal time that caused the early eaters to lose more weight.

For one, there were more women in the late eaters group, and women typically have a harder time shedding pounds. The early eaters were also described as morning people, who started their days earlier — a significant lifestyle difference that could be impacting weight loss.

Mendelson also notes that there is no data on the distribution of other meals, all we know is that the total caloric intake was the same in the two groups. Maybe the morning eaters ate in patterns that boosted their metabolism.

And lastly, the subjects were always weighed in the evening, which for some of the late eaters may have been right after they’d eaten their biggest meal of the day.

The study also found that the late eaters were more likely to have a specific gene variation that has been associated with obesity. It seems logical that this might be contributing to the group’s difficulties losing weight.

“We also need to consider that the study took place in Spain, where the day is structured very differently,” says Mendelson.

Even if early eating was an effective weight loss strategy in Spain, it might not work the same way in North America.

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“There are several plausible explanations for these very interesting results,” says Nick Bellissimo, an assistant professor and the director of the Food Intake Regulation & Satiety Testing Laboratory at Ryerson University.

Bellissimo notes that the later eaters also tended to skip breakfast.

"It is well established in the literature that this behaviour is associated with increased risk of obesity and unhealthy body weights,” says Bellissimo.

“The other obvious factor that may explain the lower body weights among early lunch eaters is that the residual effect of breakfast impacts food intake at the next meal,” says Bellissimo. “You eat less because of the physiologic satiety signals from breakfast are still present at lunch.”

So while this paper does bring to light the many complex factors that interact to affect weight loss, it doesn’t prove that eating your main meal before 3 p.m. will make you skinny.

For Bellissimo, it makes sense to stick with the factors we know will influence weight loss, without discrediting the information this study brings to light.

“The main recommendation would be to avoid the things we definitely know contribute to weight gain, like high-fat diets and breakfast skipping,” says Bellissimo. “But we have to be aware that meal timing may be an important determinant in maximizing the effects of a generally healthy diet.”