I first met Eric Ravussin 35 years ago. At that time he headed an NIH lab in Phoenix. The site of his work was coincident with the fact that the local Pima Indians have the highest prevalence of diabetes. Some say up to 50% of them do.
Shortly after his move from Lausanne Eric started his illustrious career in metabolic studies which continue to date with his affiliation with the Pennington Institute in Louisiana.
In the 1960s and 70s I had a substantial involvement in metabolic studies as well. My NIH supported research funded an inpatient protocol at the Lankenau Hospital in Philadelphia. This was entitled "the Effect of Diet on the Metabolism of Fat in Man." Like Eric my grant underwrote the provision of a metabolic unit equipped with sophisticated technology that involved precise estimation of caloric intake and output. Eric's work however expanded beyond mine in that he was able by virtue of a radar camera to provide a precise estimate of caloric expenditure.(1) Thus he measured caloric disposition as well as intake. I had championed the ideas of "Calories do Count" and "Predictability of Weight Loss"(2). I was secure in my hypotheses as was Eric except that he had a persistent observation that troubled him. He found that the caloric expenditure as revealed by radar observations revealed a deficit.(1) In other words intake seemed to exceed usage. The First Law of Thermodynamics seemed threatened. This apparent deficit could be as much as 30% of the total calories that were ingested. There was a problem.
Eric however concluded that this deficit could be resolved by invoking the non-measured energy expenditures of fidgeting. These were not captured by his technique. This central observation has since been greatly extended by other confirming studies. These provide the answer for the current deficit between intake and output. The imperative of the First Law of Thermodynamics was confirmed. This work has been iterated elsewhere.
It is also relevant to the recent attention being paid to the adverse effect of sitting on health outcomes. It may be that sitting itself might not be the issue, but rather what you do when you are sitting. If you are limp and languid then maybe you are at risk of disuse and its deficits. However, if you are a toe tapper or squirmer you are relieved of another risk factor.
Keep fidgeting, the calories that you spend may be a health benefit.
References
1)Schutz Y, Ravussin E., Diethelm R, Jequier E. Spontaneous Physical Activity Measured by Radar in Obese and Control Subjects in a Respiratory Chamber 1982 Int J. Obesity; 6: 23-28
2) Bortz W. Predictability of Weight Loss JAMA 1968, 204: 101-105.