Monday, February 04, 2019

Guest Post: What I Learned When I Actually Read That New BMJ Breakfast Study

Last week saw the BMJ's publication of a new meta-analysis on whether breakfast is useful to weight management. And, entirely predictably, it was clickbait for journalists as well as for those who believe breakfast's benefits are a myth. The question that leaped to my mind when reading the coverage was whether or not anyone actually read the study. Because to describe it as weak, at least in my opinion, would be unbearably generous. But at least one person read it. Finnish registered dietitian Reijo Laatikainen, as he published his own thoughts on his blog, and so rather than write up mine, I invited him to write an English language version here as a guest post.
Challenging deep-rooted health beliefs is always welcome and refreshing, and not something to be feared, but can the BMJ's new breakfast meta-analysis really conclude whether breakfast benefits weight management?

The meta-analysis of randomized controlled studies on breakfast skipping published last Tuesday along with a related op-ed by Tim Spector.

Both the meta-analysis and the opinion piece criticize the nutritional recommendations of many countries and organizations which promote the role of a balanced breakfast as an important part of a healthy dietary pattern. Interestingly, the role of breakfast in both of the BMJ papers is reduced to a weight management issue. Neither paper discusses other potential effects of breakfast consumption such as blood glucose control, energy expenditure, or lipid metabolism, and instead, without data, both papers seem to indirectly imply that breakfast has no health benefits whatsoever.

But back to weight management which was the scope of the study. The first sentence of the conclusions of the meta-analysis reads:
This study suggests that eating breakfast is not a good weight management strategy.
Does it though? My faith is tested.

In order to understand the effect of any strategy, dietary or otherwise, on weight management, first and foremost, the study must be long enough, ideally years, and in fact this is regularly seen with studies of different diets. For example, there are several meta-analyses of low-carbohydrate diet (LCD) RCTs with minimum durations of 6 months, and there are even studies with multi-year durations. This is appropriate of course given the question being asked is whether a particular diet has an impact on something that by definition is of long-term duration as temporarily lost weight may not stay lost forever.

This breakfast meta-analysis is not like those compiled for LCDs. Here, a total of 13 studies were included of which 4 did not last longer than a single day. In fact none of studies lasted even 6 months with the longest being 16 weeks, and the shortest just 8 hours.  Most studies lasted 1-4 weeks. When all these short, heterogenous studies were merged together, a 260 kcal increase in energy intake and 0.4 kg (0.88lb) weight gain was observed among breakfast eaters as compared with breakfast skippers.

And whether you're on team breakfast or not, I think all would agree that the studies included were of such short duration that even compiled together, they simply cannot reliably conclude anything about breakfast's utility to long-term weight management.

So what about the actual content of breakfast studied, what did the subjects eat? This is (inadequately) explained in Table 2. Commonly mentioned breakfast was juice with cereal and/or white bread. In one study, breakfast is described as follows:
"Bran cereal between 7 and 8 am, and a chocolate covered cookie between 10 30 and 11 am."
Does anyone really assume that such a breakfast would benefit weight management? In which country or organization's nutrition recommendation is such a breakfast recommended?

A few more things are worth noting. Studies on children and adolescents were excluded from the analysis. Similarly, studies of people with type 2 diabetes, where protein-rich breakfasts were shown to improve blood glucose control and reduce weight [ref, ref, and ref] were excluded from this analysis.

As a result of these shortcomings, this study clearly can't conclude anything about the impact of consuming a balanced and protein-rich breakfast on any aspect of long term health or weight management. Its conclusions are also contradicted by cohort studies which provide some information on long-term breakfast skipping which in turn suggest that skippers tend to be heavier.

Putting aside the problem with drawing long term conclusions on short term studies, at best, the most generous conclusion that can be drawn from this BMJ meta-analysis is that a low-quality breakfast does not help in weight management, and may even make it more difficult.

In order to truly decipher the role of breakfast to weight management and to health as whole, randomized trials of at least 6 months duration, with a balanced, protein-rich breakfast, are needed, and attention should be paid to its impacts on both healthy subjects as well as those with type 2 diabetes. Furthermore, changes in glucose metabolism and blood cholesterol, should be monitored as breakfast skipping might potentially worsen glucose tolerance even among healthy people and/or elevate their cholesterol.

One thing though is certain. This paper definitely does not provide even a remotely definitive answer to the breakfast question. At best, it reveals how weak the current quality of randomized breakfast studies.

PS. Just so that there's no confusion I'd like to explicitly state that breakfast is by no means a miraculous maneuver which is a categorial prerequisite for successful weight management. If you're a breakfast skipper, and your weight is managed to your satisfaction, you don't struggle with dietary restraint in the evenings, and your lipid and glucose values are within normal range, you are encouraged to continue to skipping breakfast.

Reijo Laatikainen, PhD, MBA, is registered dietitian working at Aava medical centre and Docrates cancer centre in Helsinki, Finland. You'll find him at Twitter @pronutritionist