Evening types or owls seem to suffer from social jet lag because, having gone to bed late, they are always having to wake earlier than they would like. These owls compensate for tiredness or ‘sleep debt’ during the week by lying in over the weekend, but in the meantime they suffer from stress and depression. So, for example, one study from Munich, reporting on some 500 volunteers, discovered that the more someone was an owl, the more likely they were to smoke and drink excessively.14
Equally, another study from Chicago and Bangkok, reporting on patients with type 2 diabetes, showed that the more a person was an owl (which was determined by how much extra sleep they took – and by how late they got up – at weekends) the more likely they were to skip breakfast and the more likely they were to be overweight and to have severe diabetes. They were also more likely to develop hypertension.15
These studies showed, therefore, that the breakfast skipping of social jet lag was – like the smoking and drinking and stress and depression and obesity and diabetes of social jet lag – just one of the complications of the social jet lag: the skipping did not cause the complications, it was one more to add to the list.16
The damage caused by social jet lag is mediated by sleep deprivation, but social jet lag is, of course, not the only cause of sleep deprivation, and a research group from Okayama, Japan, has shown that people who have difficulty in getting to sleep for whatever reason, or who wake up at night for whatever reason, are also two and a half times more likely to develop type 2 diabetes.17 And a recent study from Sweden on healthy young men who were kept awake artificially showed that on the following day they ate significantly more food.18
Sleep deprivation also damages by raising the levels of stress compounds in the blood including cortisol, certain pro-inflammatory chemicals and free fatty acids.19 These promote insulin-resistance and thus obesity and type 2 diabetes.20
From all these different studies, therefore, it appears that:
So we have uncovered yet one more association between breakfast skipping, obesity and diabetes which owes nothing to cause and effect but which, rather, is rooted in a common factor of sleep deprivation.fn1
Finally, a good Darwinian would be compelled to find a compensatory benefit to being an owl: if owls are less healthy than larks, they should surely have gone extinct by now, yet it has been reported that night owls are more intelligent than morning larks, which perhaps explains their survival.21
Recent (welcome) developments: As we increasingly understand the links between breakfast skipping and obesity to be an association, not causation, it’s good to report that scientists are, today, increasingly careful not to conflate them. So, for example, a 2010 overview of sixteen different European studies that found breakfast skipping and obesity to be linked nonetheless concluded that since ‘almost all of the data … were gathered from observational studies … causality should not be assumed’.22 Epidemiological sanity is beginning to win out.
Much breakfast epidemiology has only confirmed what Michael Marmot from University College London established long ago, namely that in the west the upper socio-economic groups outlive the lower groups by about seven years, probably because they experience less stress.fn2 And since the upper socio-economic groups tend to comply with the conventional advice to eat breakfast and other regular meals, while the lower groups tend to eat less regularly, much epidemiology reflects only a correlation between frequent eating and longevity.
The Harvard and Cambridge challenges
Harvard has for years been studying the 51,529 middle-aged professional white men of the Health Professionals Follow-Up Study (HPFS). These men were recruited in 1992, and it happened that some 17 per cent of them were breakfast skippers, which is a typical percentage.
At least three important breakfast-related findings concerning weight gain, type 2 diabetes and coronary heart disease have apparently come out of this politically incorrect Follow-Up Study on middle-aged upper middle-class white men:
In 2007 the scientists of the HPFS reported that ‘the consumption of breakfast may modestly contribute to the prevention of weight gain compared with skipping breakfast in middle-aged and older men’1
In 2012 the scientists reported that ‘breakfast omission was associated with an increased risk of type 2 diabetes’2
And in 2013 the scientists reported that ‘eating breakfast was associated with significantly lower coronary heart disease risk in this cohort of male health professionals’3 [all my italics].
But we would be hasty to accept the associations as causations. First, the breakfast skippers are unquestionably following risky lifestyles: men who skipped breakfast smoked three times more, exercised less, drank more coffee and alcohol, and ate significantly less healthy foods than men who ate breakfast. Breakfast skippers were also 21 per cent more likely to snack, were a bit fatter, and were more likely to eat late at night. In the 2013 coronary heart study, moreover, the researchers also found that breakfast eaters were more likely to be married (marriage is good for men’s health)fn1 and that skippers were significantly less likely to get regular health check-ups.
In their three breakfast studies, the Harvard scientists of the HPFS tried to correct statistically for those confounding factors, but I suspect they failed to do so – not because they didn’t try hard enough but because there are simply too many unknown factors. So, for example, no correction was made for social support (people with good networks of friends tend to live longer than the friendless,4 and they also tend to eat breakfast,5 which does not tell us that eating breakfast is a good way of keeping friends, nor that eating breakfast is healthy, but rather that compliance with conventional human norms such as friendship leads to better health outcomes, even if certain aspects of that compliance – viz breakfast – are unhealthy).fn2 Until correction has been made for the full panoply of risks, we simply cannot accept Harvard’s claims that breakfast is safe.
Moreover, the HPFS scientists have finally confirmed that the satiety hypothesis has been disproved, and in their 2013 paper they reported that breakfast eaters consumed 123 calories a day more than the skippers. Cumulatively, this should lead to the breakfast eaters putting on a pound of fat (0.5 kg) more, every month, than the skippers, so Harvard’s own data suggest that breakfast is unhealthy.
Yet the Harvard HPFS researchers remain wedded to breakfast