Claims that large breakfasts are good for our health have hit the headlines, with the Daily Star saying that a "Big brekkie battles obesity and disease".
But this news is based on the results of a study that assessed the health outcomes of diet in a very specific group: overweight women with metabolic syndrome.
The women were randomised into one of two groups:
- breakfast group – women were assigned to a diet where breakfast was the largest meal of the day
- dinner group – women were assigned to a diet where the evening meal was the largest meal of the day
They were given identical diets and only the timing of their largest meal differed. Both diets led to weight loss and improvements in blood sugar control, although many of these improvements were greater in the breakfast group.
However, the media assumption that these effects would lead to a consistent improvement in blood pressure and blood sugar control (which reduces diabetes risk) is not backed up by the study's findings.
The study only lasted 12 weeks, so it is not known what the long-term health outcomes associated with the recommended breakfast diet are.
There is also the crucial practical consideration of whether the women would stick to the diet in the long term or maintain any weight loss after the diet ended.
This study suggests that the timing of a meal may be important in weight loss efforts, but whether it would lead to a significant reduction in chronic disease risk is unclear. Any claims to this effect are therefore unfounded.
Where did the story come from?
The study was carried out by researchers from universities in Israel. The funding source was not mentioned, but the authors declared that they had no competing interests.
It was published in the peer-reviewed journal Obesity.
The UK media appears to have fixated on the idea that a traditional English fry-up was the recommended breakfast diet, which is not the case. The diet actually consisted of foods such as turkey breast and tuna.
Many news sources also illustrated their stories with pictures of sausages and bacon, which weren't part of the diets used in the study (unsurprisingly, given that the study's participants were Israelis).
Although the study found that the bigger breakfast improved some measures of metabolic syndrome (blood sugar control), it did not examine disease outcomes such as diabetes or high blood pressure.
What kind of research was this?
This was a randomised control trial comparing weight loss diets involving the same calorie content, but with the largest meal given either at breakfast or dinner, which was defined as a meal eaten between 6pm and 9pm.
The researchers highlight that most weight loss strategies or diets focus on reducing the overall amount of calories a person eats or drinks.
However, previous research indicates that the time of day a person eats may also be important in how the body metabolises food, as well as in weight loss.
What did the research involve?
The research involved recruiting 93 overweight or obese women with metabolic syndrome. Metabolic syndrome is the medical term for a combination of risk factors known to increase the risk of cardiovascular disease, such as:
- impaired blood sugar control, which can lead to the onset of diabetes
- high blood pressure
- high cholesterol
The average age of the women was 45.8 years, with an age range from 30 to 57. Women with serious medical conditions, pre-existing cardiovascular disease or cancer were excluded.
The women were randomly assigned to one of two diets that had the same overall calorie content (1400kcal), but differed in the timing of the largest meal of the day.
- breakfast group – 700kcal breakfast, 500kcal lunch and 200kcal dinner
- dinner group – 200kcal breakfast, 500kcal lunch and 700kcal dinner
The large 700kcal meal included two slices of whole wheat bread, light tuna in water, skimmed milk, a bar of milk chocolate, sweet tomato, basil and mozzarella salad, and a grande americano coffee. The meals were the same for the two groups, regardless of whether they were eaten at breakfast or lunch.
Participants were asked to eat breakfast between 6am and 9am, lunch between noon and 3pm, and dinner between 6pm and 9pm.
The women were asked to remain on the diet for 12 weeks. Over the 12 weeks, the researchers measured changes in weight loss, waist circumference and a range of measures related to their metabolic syndrome, such as blood insulin levels and blood fat levels, to see if there were any improvements.
Changes in weight and measures of metabolic syndrome were compared between the breakfast and dinner group for statistically significant differences that could indicate which diet might be better.
What were the basic results?
Both groups lost weight and reduced their waist circumferences on the 1400 kcal diets. The main result, however, was that the breakfast group showed greater weight loss and waist circumference reduction than the dinner group.
Weight loss over the 12 weeks was 8.7kg in the breakfast group compared with 3.6kg in the dinner group, a difference of 5.1kg. Over the same period, waist circumference decreased 8.5cm in the breakfast group compared with 3.9cm in the dinner group, a difference of 4.6cm. Both differences were statistically significant, suggesting they weren't due to chance alone.
Many measures of metabolic syndrome improved in both groups on the 1400kcal diet. However, the breakfast group had significantly greater improvements in fasting blood sugar, insulin levels and insulin resistance (linked to diabetes).
The researchers also found that average hunger scores and fullness scores (feeling satisfied after eating) were significantly better in the breakfast group compared with the dinner group.
How did the researchers interpret the results?
The researchers concluded that, "a high-calorie breakfast with reduced intake at dinner is beneficial, and might be a useful alternative for the management of obesity and metabolic syndrome".
This dietary study found that overweight or obese women with metabolic syndrome lost weight on a specified controlled diet. They also seemed to have greater improvements in their blood sugar control when their main energy intake was at breakfast, compared with the same diet where the main energy intake was at dinner.
This lends support to the old adage that you should "breakfast like a king, lunch like a prince and dine like a pauper", as well as the theory that the timing of food intake may be important in people's efforts to lose weight.
This is something that does not have a high profile in current diets and weight loss efforts, which tend to focus on the number of calories consumed overall, irrespective of the time of day people eat their main meal.
Overall, the research was generally good quality, but has some limitations to be aware of.
Small sample size
The study's main drawback is that it only recruited 93 women, so it can only tell us so much about people and their weight loss efforts in general. The women were also all middle-aged and free of other major medical conditions, including existing cardiovascular disease.
It therefore tells us nothing about the effect of meal timing for men, women of other ages or people with other medical conditions who may also want to lose weight. The effect may be similar, but it would need to be studied directly to be sure.
Length of study
The effects of the diet were assessed in the short term during the 12-week study. There was no longer term assessment of whether eating a big breakfast reduces any disease risks or risk of death from cardiovascular diseases.
Similarly, it wasn't clear if the women were able to incorporate the diet into their lives long term, or whether it was more of a short-term weight loss intervention. It is common in dieting for people to put weight back on as soon as the diet stops because they return to their old habits. The key is making sustainable healthy lifestyle changes long term, rather than "yo-yo" dieting.
Encouragingly, it appeared that slightly more women were able to stick to the breakfast diet for 12 weeks (17% dropped out because they stopped following the diet) than the dinner diet (23% dropout) over the same period. This suggests the big breakfast approach is practical and was adopted without too much trouble by the women in the study.
This study suggests that current dietary interventions should consider meal timing as an important factor and not solely focus on overall calorie intake. However, because the study was small, it would be inappropriate to start making recommendations or snap changes to existing dieting programmes based on this research alone.
A final point is that the media's suggestion that a traditional British fry-up is good for you is not borne out by the study. Regularly eating items such as fried bacon and sausages will increase your cholesterol levels, putting you at increased risk of cardiovascular disease. Healthier breakfast options include porridge and muesli.
Read more about healthy breakfast recipes.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
Daily Star, 7 August 2013
Mail Online, 6 August 2013
Daily Express, 7 August 2013
Links to the science
Obesity. Published online March 20 2013