Monday January 7 2008
Not a licence to eat fry ups
“Breakfasting like a king and dining like a pauper really is the answer to middle-age spread”, the Daily Mail reported January 4 2008. The newspaper said that a study has found that “whether a person has breakfast or not may affect weight gain more than the amount of food eaten throughout the day”.
The news story is based on a well-conducted cohort study in Norfolk that found that people who consumed more of their day’s total energy at breakfast had smaller weight gain than those who ate less in the morning.
The study corroborates the accepted wisdom that eating breakfast has health benefits. However, any dietary advice on the back of this should again emphasise what is known about the association between saturated fats and the risk of cardiovascular disease - too many fry ups for breakfast are still bad for your heart.
Where did the story come from?
Dr Lisa Purslow and colleagues from Addenbrooke’s Hospital and other medical institutes from London and Cambridge carried out the study. Funding was provided by Cancer Research UK, the Medical Research Council, the Stroke Association, the British Heart Foundation, the United Kingdom Department of Health, Europe Against Cancer Program Commission of the European Union, Food Standards Agency, and the Wellcome Trust.
The study was published in the peer-reviewed: American Journal of Epidemiology.
What kind of scientific study was this?
The study used data from a subset of people who took part in a large prospective cohort study of men and women aged 40 to 75 living in Norfolk. People signed up to the study between 1993 and 1997, when they had their weight and height measured (to calculate their body mass index – BMI) and completed a health and lifestyle questionnaire (which included an assessment of smoking levels, physical activity, social class and other details).
At the beginning of the study the participants also filled in a seven day diary to record their food intake each day, which the researchers then used to calculate the total daily energy intake and the proportion of the energy that was taken in at different times of the day (e.g. breakfast, lunch, dinner).
The participants were contacted again between 1998 and 2000 (an average of about 3 years later), to have their height and weight measured and to be asked the health and lifestyle questions.
The researchers then determined whether weight change between the start of the study and the follow-up was linked to the amount of energy consumed and the time that the energy was consumed during the day (e.g. at which meal times). To do this, they divided the percentage of energy consumed at different times of the day into five equal groups (called quintiles) and compared those who consumed the least amount of their total daily energy at breakfast time with those who consumed the most.
This particular publication reports on the 6764 people who had information available from food diaries.
What were the results of the study?
The researchers found that all participants gained weight during the course of the study and that the proportion of energy consumed at breakfast ranged from 0% of the total daily intake to 50% of the total daily intake.
The study found that people who consumed 22 to 50% of their energy at breakfast had the lowest BMI compared to people who consumed only 0 to 10% of their energy at breakfast. They found that a 1% increase in the proportion of total energy consumed at breakfast time was associated with 21g less weight gain.
What interpretations did the researchers draw from these results?
The researchers say that their findings indicate that consuming a “higher proportion of total daily calories at breakfast is associated with relatively lower weight gain in middle age”.
They put forward some possible biological reasons why this might be the case, including a theory that skipping breakfast results in increased levels of insulin when food is finally taken in. They say that this increased insulin may lead to increased fat storage and weight gain.
What does the NHS Knowledge Service make of this study?
This is a well-conducted study, but the study’s design limits the interpretation of its findings.
- The best way to answer a question such as “does eating breakfast lead to health improvements?” (e.g. reduced weight gain or other benefits) is through a randomised controlled trial. As with all cohort studies – the design used in this study - there is a chance that factors that have not been measured and taken into account may be behind the association. The authors adjusted for some factors that may be responsible for a link between breakfast energy intake and lower weight gain, but they admit that they cannot rule out the effects of unknown factors. For example, they did not make any adjustment for health status.
- Importantly, food intake was only measured at one point at the beginning of the study. The pattern of food intake is unlikely to have remained the same for each individual over the years that the study lasted. Those people whose dietary patterns had changed over time would be wrongly classified in the final analysis and this would have biased the results. In addition, the researchers themselves say that all dietary recording methods are associated with under-reporting, particularly by obese people.
- The study did not consider which types of food were being taken in at different meal times. “Big breakfasts” don’t necessarily mean unhealthy ones. There is no factual basis to interpret this to mean that a fry up in the morning is good for you and existing advice to avoid eating too much fat should be followed.
This research confirms the findings of other studies, that breakfast is a good meal and that consuming a healthy breakfast in the morning is beneficial. Any dietary advice arising from this study should include what is known about the links between a diet high in saturated fats and the risk of cardiovascular disease. As a spokesman from the National Obesity Forum is quoted in the Daily Mail “Breakfasts won’t help you lose weight if they’re full of black pudding and fried bacon”.
Sir Muir Gray adds...
As someone whose breakfast is an apple when walking to the bus stop, I am perhaps not the best person to comment. But I wont swap the walk for a breakfast, and I wont get up any earlier to accommodate both. I have nothing against breakfast, but not everyone can fit it into their lifestyle.