Tuesday July 23 2013
There is a general consensus that skipping breakfast is a bad idea
"Breakfast is the most important meal of the day," reports the Daily Mail, claiming that "skipping it increases your chances of a heart attack."
The news comes from a 16-year study of a large group of middle-aged and older male American health professionals, their eating habits, and their risk of developing coronary heart disease. It found that men who reported skipping breakfast had a 27% higher risk of coronary heart disease than men who ate breakfast.
Men who regularly indulged in a "midnight snack" (getting up to eat after they had gone to bed) were found to have a 55% higher risk of coronary heart disease than men who didn't.
However, no association was seen between eating frequency (number of meals per day) and the risk of coronary heart disease. This could suggest that it is the timing of meals rather than the frequency that has a bigger influence on heart health.
But because of the design of this cohort study, a direct cause and effect relationship between breakfast and health cannot be proven. While the researchers attempted to take certain lifestyle factors into account, it could be the case that people who take time to have a regular breakfast also tend to have healthier lifestyles.
The population being studied was also extremely limited – professional men who were almost exclusively white. More research in women and other groups is needed for us to learn more about breakfast and heart health.
Where did the story come from?
The study was carried out by researchers from the Harvard School of Public Health, Brigham and Women's Hospital and Harvard Medical School. It was funded by the US National Institutes of Health and the Canadian Institutes of Health Research.
The study was published in the peer-reviewed journal Circulation.
This research was widely covered in the UK media and was well reported.
What kind of research was this?
This was a cohort study that followed a large group of male American health professionals to see whether self-reported eating habits, including skipping breakfast, are related to an increased risk of developing coronary heart disease.
Cohort studies cannot prove cause and effect, as it is not possible to exclude the possibility that there are other factors (confounders) responsible for any of the associations seen.
Nevertheless, it is the ideal study design for addressing this question, as it would be difficult to randomly allocate a large group of people to either eating or not eating breakfast for a long period of time.
This study is also limited by the fact that participants were only asked about their eating habits once, at the start of the study, and their eating habits could have changed during the course of the study. No details about the exact timing or specific composition of meals and snacks were collected.
What did the research involve?
This study followed a cohort of 26,902 male American dentists, vets, pharmacists, optometrists, osteopaths and podiatrists aged between 45 and 82 years old for 16 years. To be eligible for the study, the men could not have a history of cancer, coronary heart disease, angina, heart attack or stroke.
At the start of the study, participants were asked the following question: "Please indicate the times of day that you usually eat (mark all that apply): before breakfast, breakfast, between breakfast and lunch, lunch, between lunch and dinner, dinner, between dinner and bed time, and after going to bed."
The researchers categorised men who reported eating before breakfast, at breakfast or between breakfast and lunch as "eating breakfast".
Men who said they eat after going to bed were categorised as "late-night eaters".
The men were then followed up to see whether they developed coronary heart disease.
The researchers assessed whether eating breakfast, late-night eating, other individual meals and snacks, and eating frequency were related to the risk of coronary heart disease.
When doing these analyses, the researchers adjusted for:
- diet factors – energy intake, diet quality and alcohol intake, assessed using a food-frequency questionnaire every four years; and eating frequency per day assessed at the start of the study
- demographic factors – smoking status, marital status, full-time work status, physical examination within the last two years and family history of coronary heart disease before 60 years of age, assessed every two years
- activity – physical activity, television watching and sleep, assessed every two years
What were the basic results?
At the start of the study, 13% of men reported skipping breakfast, and 1.2% reported late-night eating.
During follow-up, 1,527 men (5.7%) developed coronary heart disease.
After adjusting for diet, demographic factors and activity:
- men who did not eat breakfast had a 27% higher risk of coronary heart disease than men who ate breakfast (relative risk 1.27, 95% confidence interval (CI) 1.06 to 1.53)
- men who ate late at night (after they had gone to bed) had a 55% higher risk of coronary heart disease than men who didn't (relative risk 1.55, 95% CI 1.05 to 2.29)
- no association was observed between eating frequency and risk of coronary heart disease
The associations seen between skipping breakfast or eating late at night and coronary heart disease may be caused by other health problems, such as obesity, high blood pressure, high cholesterol levels and diabetes. This is because the associations were no longer significant if these factors were adjusted for.
How did the researchers interpret the results?
The researchers concluded that, "Eating breakfast was associated with significantly lower coronary heart disease risk in this cohort of male health professionals."
This large cohort study of middle-aged and older male American health professionals has found that eating breakfast and not eating after going to bed are associated with a lower risk of coronary heart disease.
As this was a cohort study, it cannot prove cause and effect, as it is not possible to exclude the possibility that there are other factors responsible for any of the associations seen.
The results remained the same when researchers adjusted for diet, demographic factors and activity level, but were no longer significant if the researchers adjusted for obesity, high blood pressure, high cholesterol levels or diabetes.
This suggests that the associations seen between skipping breakfast or eating late at night and coronary heart disease may in fact be because of obesity, high blood pressure, high cholesterol levels and diabetes – all known risk factors for heart disease.
The researchers speculate that regularly missing breakfast could disrupt the normal functioning of the metabolism, as well as circadian rhythms ("body clock"). Both factors could increase the risk of developing one or more of the risk factors listed above, though this remains purely speculative.
It is also difficult to exclude the possibility that eating regular meals such as breakfast is a marker of a conscious effort to lead a healthier lifestyle.
This study is limited by the fact that the men were only asked about their eating habits once, at the start of the study, and their eating habits could have changed during the course of the study. Details about the exact timing or specific composition of meals and snacks were also not collected – in this study, breakfast was defined as any meal eaten before lunch.
This trial was performed in middle-aged and older male American health professionals, who on average had a good quality diet. Further research is required to see if the findings are the same in other population groups, for example women or populations with poorer diets.
Despite these limitations, this study provides further evidence of the health benefits of eating breakfast.
More information on eating a healthy diet can be found in the NHS Choices Healthy eating hub.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.