"People who are too fat or too thin are 'more likely to suffer from migraines'," reports The Sun.
Researchers reviewed data from 12 studies involving 288,981 people and concluded obese people have a 21% increased risk of migraines, compared to those of healthy weight.
Migraines are moderate to severe headaches that are more common in women. People who are underweight also have a small increased risk.
Researchers don't know exactly how weight affects migraine risk, but it may be to do with chemicals released by fatty tissue. Researchers found that both age and sex affected people's chances of the condition, as well as their weight.
This type of research can't tell us whether migraine is caused directly by weight. And we don't know whether obese people with migraine can lower their chances of having the painful headaches by losing weight.
Read more about how to lose weight safely with the NHS Weight Loss Plan.
Where did the story come from?
The study was carried out by researchers from Harvard TH Chan School of Public Health and Johns Hopkins University School of Medicine in the US, the University of L'Aquila in Italy, and the University of Queensland in Australia.
The researchers reported no direct funding. The study was published in the peer-reviewed journal Neurology.
The Sun gave an accurate overview of the study. The Mail Online's rather odd headline claimed that: "Being a healthy weight is the only way to beat migraine," ignoring the fact that many people of healthy weight get migraines, and there are plenty of migraine treatments around.
The Mail also said that "migraine sufferers could prevent the misery of migraine headaches by staying at a healthy weight," when the research does not show that changing weight affects migraine.
Both newspapers use the researchers' figure that obesity leads to a 27% greater risk of migraine, based on an analysis adjusted for age and sex. However, the fully-adjusted figure, taking into account multiple risk factors for migraine, is 21%.
What kind of research was this?
This is a meta-analysis, which pooled results from previously-published studies looking at links between weight and migraine. Meta-analyses are a good way of summarising all the existing research about a topic. However, they are only as good as the studies that they report.
All of the studies in this case were observational in nature, and so are not able to show that being over- or underweight causes migraines.
What did the research involve?
Researchers looked for previously-published observational studies on migraine and weight. They pooled the data to look for links between migraine risk and different categories of weight – underweight, healthy weight, overweight or obese. They adjusted their figures to take account of confounding factors known to affect migraine risk, such as age and sex.
The studies included were assessed to be of fairly good quality (all ranking seven or above on a 10-point quality scale).
The researchers conducted sensitivity analyses to ensure the pooled results were not skewed by any individual study. They also asked the original study authors for additional information, meaning they were able to include data not used in previous meta-analyses.
What were the basic results?
The study found that obese people and underweight people, but not overweight people, were more likely to report having migraines.
Compared to people of healthy weight:
- obese people were 21% more likely to have migraines (odds ratio [OR] 1.21, 95% confidence interval [CI] 1.08 to 1.34)
- underweight people were 12% more likely to have migraines (OR 1.12, 95% CI 1.03 to 1.21)
Both the chances of having migraines, and the link between migraines and obesity, were strongest in younger people and lessened with age.
How did the researchers interpret the results?
The researchers say their findings show a potential "moderate" increased risk of migraine from being obese. They say this finding "supports the need for research to determine whether interventions to reduce obesity decrease the risk of migraine".
They suggest this will help scientists understand the causes of migraine better, and possibly develop treatments based on people's weight.
The study results are clear: people who are obese have a moderately increased chance of getting migraine headaches, and people who are underweight have a small increased chance. However, the results don't tell us why that is.
There are a few limitations to be aware of:
- More than half the studies used people's self-reported height and weight to calculate body mass index, which may have under-estimated the proportion of people who were overweight.
- Half the studies used people's self-report of migraine, rather than a medical diagnosis, which could have affected the accuracy of the results.
- There were substantial differences between the included studies, this reduces the reliability of the combined results.
The link to weight is likely to be only one factor contributing to whether someone gets migraine, including genes inherited from parents. Lots of things have been identified as possible triggers for migraine headaches in those susceptible, including:
- hormonal changes (many women find they are more likely to get migraine around the time of their period)
- diet (some people report migraines after eating specific food such as cheese, or when they skip meals)
- emotional states such as anxiety, depression or shock
- tiredness and lack of sleep, or shift work
- environmental factors such as bright lights or changes in the weather
While it's always a good idea to keep to a healthy weight (it's not called a healthy weight for nothing), we don't know from this study if losing weight (for obese people) or gaining weight (for underweight people) will affect their chances of getting migraines.
Avoiding the triggers listed above, when possible, should also help.
Read more about migraine prevention.