Longevity Briefs: Another Study Warns Against Meal-Skipping

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: Previous studies have suggested that people who skip breakfast live shorter lifespans. We’ve previously reported on this kind of study and why they can’t always be taken at face value. Back in August, a new study on meal skipping was published, and it looks to be more convincing than many of its predecessors. Let’s take a look at the findings.

What did the researchers do: In the study, researchers looked at data from about 24 000 adults (all 40+ years old) who participated in the National Health and Nutrition Examination Survey (NHANES) between 1999 and 2014. This is a survey that collects health and dietary information from a representative sample of the US population in two year cycles. As part of this survey, participants were interviewed and asked to recall in detail their food consumption over the previous 24 hours, including what time the food was eaten. They were also asked to label each meal as breakfast, lunch, dinner, snack, drink and so on. This decision was left entirely up to the participants.

Researchers then followed participants over the duration of the study. After controlling for confounding factors like age, gender, income, diet and other health practices, they looked to see if there was a relationship between whether participants skipped important meals and whether they died from any cause or from cardiovascular disease specifically during the study period. They also investigated whether the length of time between major meals had an impact on these health outcomes.

Key takeaway(s) from this research:

• After fully adjusting for confounding factors, eating only 1 meal per day was associated with a significant increase in mortality: a 30% increase for all-causes and an 83% increase for cardiovascular disease specifically when compared to eating 3 meals per day.
• Skipping a single meal was associated with a 12% increase in all-cause mortality if that meal was lunch, and a 16% increase if that meal was dinner. The largest effect was for breakfast and cardiovascular disease mortality – participants who skipped breakfast had a 40% increased risk of death from cardiovascular disease during the study.
• Finally, researchers found that for participants eating 3 meals per day, gaps of 4.5 hours or less between meals were associated with 17% increase in all cause mortality compared to gaps of 4.6-5.5 hours. Larger gaps weren’t associated with a significant increase in mortality.

Compared to most previous studies, this study is a step up for multiple reasons. It was large, and the information collected was relatively detailed, allowing the effects of skipping each meal to be evaluated. The study also controlled for a good number of potential confounding factors including calorie intake, exercise, snack frequency and health status at the start of the study.

We still need to be mindful that this was an observational study. We went into more detail about what an observational study is and what their limits are in this article. In brief, when you divide people into two groups based on some predetermined factor (such as whether or not they eat breakfast), you are already comparing two groups that are likely to be different in other ways. For example, people who skip breakfast are more likely to smoke, drink, and have lower incomes on average. This means that the mortality of each group must be adjusted to account for such differences, but these adjustments are not perfect, and we cannot know for certain that some of the increased mortality from meal skipping was not due to these other factors.

Some confounding factors were not controlled for, most notably sleep. We know that sleep quality, duration and timing can affect appetite throughout the day, so it’s a shame that the relationship with sleep couldn’t be studied. The fact that participants were asked to recall what they ate over the last 24 hours and to label meals themselves could also have introduced bias into the results. You are unlikely to forget that you skipped lunch the previous day, but you could easily forget about the compensatory chocolate snack you ate while waiting for the bus.

With all that being said, it’s hard to discount the sizeable effect of breakfast skipping in its entirety. This study certainly shifts the balance of evidence in favour of eating three meals a day, preferably spaced around 5 hours apart or more. It is worth pointing out that when meals including breakfast are skipped for the purposes of reducing calorie intake, randomised clinical trials still suggest that this practice is beneficial overall, at least over the short duration of such trials. However, perhaps we should be cautious about meal-skipping as a long term way of reducing calorie intake.