Long Live Weekend Warriors

In this edition of The Rundown, it's good news for weekend warriors, researchers chart the cellular processes modified by exercise and why you should avoid the midnight snack.

The Rundown

Long Live Weekend Warriors. A recent study published in JAMA Internal Medicine reveals that when it comes to living longer, exercising only on the weekend is enough to make up for a sedentary lifestyle during the week—as long as you hit the recommended guideline of 150 minutes of moderate-intensity aerobic activity.

The study examined data from over 350,000 U.S. adults who self-reported their physical activity on a yearly basis from 1997-2013. People were classified as physically inactive, “weekend warriors,” or “regularly active” based on the frequency, intensity and duration of their exercise.

To track mortality, the researchers cross-referenced the National Death Index through December 31, 2015.

They found no statistically significant difference in mortality rates between weekend warriors and regularly active participants. Both groups had lower mortality rates than the inactive group, even when broken down between all-cause, cardiovascular disease and cancer mortality.

The study’s limitation is that it relies on self-reported activity levels. It also doesn’t reveal whether weekend warriors have the same fitness improvements as regular exercisers or if they are more prone to injury.

Still, the comparable health benefit is good news for those who find it hard to spread their physical activity across the week.

Charting Exercise and High-Fat Diet. We know that exercise helps us lose weight and avoid gaining it but the cellular mechanisms that are part of this process have been difficult to identify simply because there are so many cells and tissues involved.

In a new study, researchers from MIT and Harvard Medical School have taken an important step toward changing this by mapping out many of the cells, genes and pathways that are modified by exercise or a high-fat diet. Their findings may offer potential targets for drugs that could help to strengthen or even mimic the benefits of exercise.

The team studied mice with high-fat or normal diets that were sedentary or allowed to exercise whenever they wanted. They used single-cell RNA sequencing to catalogue the responses of 53 types of cells found in skeletal muscle and two types of fatty tissue.

Senior author Manolis Kellis says the study’s findings show the major effect that exercise has throughout the body. “One of the general points that we found in our study, which is overwhelmingly clear, is how high-fat diets push all of these cells and systems in one way, and exercise seems to be pushing them nearly all in the opposite way.”

Hold the Midnight Snack. Does the time we eat matter when everything else is kept consistent? A team of investigators from Brigham and Women’s Hospital wanted to find out in a new study that looks at the effects of late eating on calorie intake, calories burned and molecular changes in fat tissue.

They found that eating four hours later makes a big difference in our hunger levels, the way we burn calories after we eat and how we store fat.

The team studied 16 people with a BMI in the overweight or obese range. Each person completed two in-laboratory protocols: a strict early meal schedule and a schedule of those same meals scheduled about four hours later in the day.

Before starting the in-lab protocols, the participants kept fixed sleep and wake schedules. Three days before entering the lab they followed identical diets and meal schedules at home.

Once in the lab, the volunteers kept a record of their hunger and appetite, gave small blood samples throughout the day, and had their body temperature and energy expenditure measured. To find out how eating time impacted the molecular pathways involved in how the body stores fat, the team conducted biopsies of adipose tissue from a subset of participants.

The researchers discovered that eating later had significant effects on the hunger and appetite-regulating hormones leptin and ghrelin, which influence our desire to eat. Levels of leptin, which signals feeling full, decreased across the 24 hours in the late eaters compared to the early eaters. When the participants ate later they also burned calories at a slower rate and exhibited molecular mechanisms that promote fat growth.

Replay

This week’s vintage moment in sport’s culture is brought to you by a horizontal Dennis Rodman. Pacers at Bulls, March 7, 1997. Photo: Sam Forencich/NBAE/Getty Images.