When You Eat May Trump What You Eat for Weight Loss


"Cut back on calories" seems to be the dietary mantra when it comes to reducing weight.

However, a study on mice published Thursday in the Journal of Cell Metabolism suggests that losing weight may have less to do with watching calories - and more to do with watching the clock.

"For millions of years, we humans spent our lives as diurnal species - eating most of our calories only in the daytime and fasting overnight," said Satchin Panda, associate professor at the Salk Institute for Biological Studies in La Jolla, Calif., and lead author on the study. "In the last one hundred years or so, we have started to stay up at night and consume calories at night too. During this time, we have also observed an increase in the cases of diabetes and obesity."

This study found that mice that consumed as many calories as they wanted for eight hours and fasted for the remaining 16 hours were essentially the same as mice that ate a healthy diet when it came to gaining weight, diabetes risk and high cholesterol.

"The gist of this study is that the timing and the number of hours you fast impact your weight gain," Panda said. "Watch the times of day you eat as opposed to what exactly you eat. You don't have to be as strict in counting calories."

So what does this mean for humans wanting to lose weight and reduce their risk for diabetes and high cholesterol?

Dr. Darwin Deen, professor at City College of New York, said he is cautious of these findings and translating a study on mice to humans.

"In all of human history, there are more calories now to get fat with," he said. "Now, when we wake up in the morning, the question isn't, 'Is there food to eat?' but 'What would you like to have for breakfast?'

"Perhaps the best conclusion from this study is eating at night is not the best idea and having a more regulated diet is something we need to aim for."

Keith Ayoob, associate professor in the department of pediatrics at Albert Einstein College of Medicine, has similar thoughts. "Mice are mice. Humans work differently," said Ayoob. "A high-calorie diet in eight hours can be a slippery slope. Almost like a loaded gun." His advice?

Ayoob suggested eating a balanced diet - three meals a day with a snack. Breakfast eaters control their weight better than those who go for longer periods without eating and in turn, gain more weight.

Additionally, he said, long-term weight management needs an activity component.

"Move! We focus a lot on food and diet but activity is deal breaker."

Dr. George Blackburn, associate director of the division of nutrition at Harvard Medical School, advises that developing a routine with a structured eating pattern is key. For example, it is important to eat breakfast because people are most active between breakfast and dinner, so calories are easily burned. The last meal should be eight to 10 hours after breakfast.

"This is a report that gives us one piece of knowledge that is valuable to us - have a time- restricted eating pattern that begins with breakfast," Blackburn said.

Ultimately, Panda feels that this study shows that reducing the number of hours during which we eat and increasing the number of hours we fast can have significant effects on weight and risk for diabetes and high cholesterol.

"Over the last 50 years, we have come up with two lifestyle interventions for diabetes prevention - reduce caloric intake and increase exercise," he said. "What we find today is that the calories in breakfast are different than the calories consumed in a midnight snack. Not all calories are created equal."