In statistical studies of health, considering the life histories, longevity, and mortality rates within a large group of individuals, researchers have found that calorie restriction and exercise have positive effects on long-term health that are large in comparison to all other positive influences measured to date. No widely available medical technology can yet grant even a sizable fraction of the additional healthy years of life that are available for free through the adoption of a better lifestyle. The most important goals in medicine - and all technology for that matter - for the next few decades involve making that last statement a thing of the past. That will involve finding ways to rejuvenate the old and extend healthy life far beyond what can be attained through today's technologies and techniques.
Meanwhile, the size of the influence of calorie restriction and exercise means that we have to eye every study in laboratory animals to see whether the researchers have accounted for differences between their groups. In human epidemiological studies, we have to ponder whether the researchers are correctly adjusting their results for these influences, or whether the associations that they identify between health or longevity and other characteristics are in fact just reflections of a deeper relationship with calorie intake or exercise.
In recent years a number of studies have claimed relationships between human mortality rates and various character traits. Researchers have standardized measures of personality, and those can be matched up with mortality in a range of different study data sets to show that some types of personality tend to live longer. One explanation is that this all comes to down to, say, ability to earn, and is thus just another facet of the standard issue correlation between wealth and longevity. Another theory is much the same, except replace wealth with conscientiousness and its effects on health maintenance.
But might it all be largely a matter of correlations with calorie intake? In a society in which calories are easy to come by, where in fact we need to actively refrain from eating more than is good for our long term health, the correlation between character and long term health might be much more pronounced than in past centuries. Yet this is only because calorie intake is such a strong determinant of the trajectory of health and mortality across a life span. So it is interesting to see people finding correlations between diet and personality:
We set out to study the associations between personality traits, resilience and food and nutrient intake in 1681 Finns in late adulthood. As hypothesized, neuroticism was associated with mainly poorer dietary quality as the intakes of fish and vegetables were lower and intake of soft drinks was higher, but this applied to women only. In line with our hypothesis, we observed extraversion being e.g. associated with a higher vegetable intake in women. Openness was associated with higher intakes of vegetables and fruits in both genders. Agreeable women showed favorable trends, as did conscientious women, the latter reporting e.g. a higher fruit intake. Some of these trends were further strengthened when testing subjects with resilient vs. non-resilient personality profiles; resilient women reported higher intakes of vegetables, fruits, fish, and dietary fiber and lower intake of alcohol. Our results were in line with our original study hypothesis and the associations were not due to age, educational attainment, or total energy intake.
Our result that neuroticism was associated with several unfavorable dietary intakes is consistent with two previous cross-sectional studies. One study in Japanese students found neuroticism to be associated with intakes of sweet and salty foods while a Scottish study found, high neuroticism to be associated with a traditional convenience diet (eating more tinned vegetables, meat pies, pasties and sausage rolls, puddings etc.) and low neuroticism to be associated with a Mediterranean-style diet. A recent Estonian study also found low neuroticism to be associated with a health aware dietary pattern. Our results are also in line with findings showing that high neuroticism is associated with obesity, metabolic syndrome and an increased risk for [cardiovascular_disease].
This study doesn't have anything to say about calorie level variations, but one might assume that where there is variation in constituents there will also be variation in calories.