Is Grazing Making You Fat?

Eating throughout the day fuels your body. But if you’re watching your weight, don’t snack late.

How many runners only eat just three meals a day? It’s more like breakfast, lunch, pre-workout, post-workout and dinner – with possibly a few snacks sprinkled in between. After all, eating mini-meals throughout the day keeps you fuelled for your workouts and stabilises your blood sugar levels. But, research published in the journal Cell Metabolism suggests that grazing – especially if it extends into later evening hours – could be preventing you from losing weight.

For the study, researchers with the Salk Institute in California had more than 150 men and women to track everything they ate – and the timing of their meals – for three weeks. They found that, on average, the participants ate over a course of 15 or more hours per day. And when overweight individuals in the study cut back their food intake to a 10- or 11-hour period, they lost an average of 3.5 per cent of their body weight over 16 weeks.

“Simply put, the more hours we eat in a day, the more time we have to over-consume kilojoules,” said dietitian Alyssa Tyler. So, if you cut the number of hours you’re “allowed” to eat every day, you wind up eating fewer kilojoules, which can lead to weight loss.

Timing also plays a role. The average person in the study consumed less than a quarter of his or her kilojoules before noon – but more than a third after 6pm. Previous research suggests that the more you eat at night, the greater your chances of being overweight. That’s largely because the foods we eat in the evening rarely tend to be healthy, said sports dietitian Georgie Fear, author of Lean Habits for Lifelong Weight Loss . Instead, it’s ice cream and potato chips munched mindlessly in front of the TV. “Plus, it’s possible that even when kilojoule intake is controlled, eating in the evening may be less than metabolically desirable,” she said.

For instance, a 2013 animal study in Current Biology suggests that at night, your body’s cells become more resistant to insulin. That means, overeating when your internal clock says it’s bedtime, not mealtime, could contribute high blood-sugar levels and, over the long term, fat accumulation and weight gain. That may explain why previous research published in the International Journal of Obesity shows that even when they eat the same number of kilojoules, people who eat most of their kilojoules earlier in the day lose more weight on their diets than do people who eat later in the day.

What’s more, to keep your metabolism healthy, you need to fast overnight (something those 15-hour grazers in the study were interfering with), Tyler said. Throughout an overnight fast, the body shifts from breaking down primarily carbs to breaking down primarily fatty acids for energy. Called metabolic flexibility, this ability to switch from one fuel source to another, is crucial for health blood sugar regulation. “So in addition to helping reduce kilojoule intake, confining your eating to 10 or 12 hours a day helps you complete nightly fasts, maintain metabolic flexibility, and regulate your blood sugar levels,” she said.

So what’s a ravenous – but weight conscious – runner to do? You can, and should, still eat in mini-meals throughout the day to fuel your body and your training. But it’s important to make sure that those meals don’t fall too late in the day, Tyler said. You do need to eventually cut yourself off and consider the kitchen closed. Fear recommends fasting for at least 10 to 12 hours per night.

Run at night? You can still have a post-workout snack. Just keep it healthy, watch the portion size, and don’t let it turn into an all-you-can eat refrigerator raid.


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