Letter to the Editor: “Twice as High Diet-Induced Thermogenesis After Breakfast vs Dinner on High-Calorie as Well as Low-Calorie Meals”

To the Editor

We read with great interest the recent article by Richter et al that compared the effect of high- versus low-calorie meals for breakfast or dinner meals on diet-induced thermogenesis (DIT) (1). Although we applaud the rigorous design and conduct of this study, we believe that the methods used to determine DIT led to a bias in the interpretation of the results. In their study, DIT was defined as difference between postprandial energy expenditure (EE) and the “resting energy expenditure (REE)” 45 minutes prior to the consumption of the dinner meals (1). However, while REE before breakfast was measured after an overnight fast, the preprandial REE measurement before dinner was only 4.5 hours after the consumption of the lunch meal. Because DIT extends at least 6 hours following the consumption of a meal (2), this contributed to a higher baseline EE prior to dinner. Because the EE patterns following breakfast and dinner were nearly identical (Fig. 1 in (1)), the lower DIT following dinner is likely the direct result of the subtraction of a higher baseline EE. In our opinion, it would be more appropriate to calculate DIT as the difference between postprandial EE after the breakfast and dinner meals and the (true) REE measured in the morning. When calculated in this manner, our view of the data is that there would be a minimal difference in DIT between breakfast and dinner. It is also worth noting that DIT following the low-calorie dinner meal was negative (Fig. 3D in (1)), which is physiologically implausible, especially considering that the circulating hormones and glucose were still elevated.

Another point to consider is the duration over which postprandial EE measurements were obtained. In their study, Richter et al measured postprandial EE for 3.5 hours after each meal (1). As demonstrated by Hill and Reed, DIT measured for 4 hours is 10% to 20% less than DIT measured for 6 hours, regardless of meals size (2). Indeed, based on Fig. 3B in (1), we estimate that DIT following the high-calorie breakfast was ~231 kj, or ~5% to 6% of the energy content of the meal, which is below the typically reported values of ~10% (3). As stated by Hill and Reed, “there (may be) important information contained in the remaining unmeasured TEF” (2).

One final point regarding the absolute values of DIT is that, based on the data in Fig. 3B in (1), the estimated cumulative DIT was ~231 kj (~55 kcal) following the high-calorie breakfast and ~126 kj (~30 kcal) following the high-calorie dinner (1). Thus, even if these differences were realized, the absolute impact on energy balance is minimal. We contend that the conclusion forwarded in the abstract (“identical calorie consumption lead to a 2.5 times higher DIT increase in the morning than in the evening after high-calorie and low-calorie meals”) inflates the findings. We are concerned with how this conclusion will be interpreted by the press and lay public.

We suggest that future studies in this area carefully consider these methodological issues when addressing this outstanding research question.

Additional Information

Disclosure Summary: Dr. Melanson is supported by resources from the Geriatric Research, Education, and the Clinical Center at the Denver VA Medical Center. The contents do not represent the views of the U.S. Department of Veterans Affairs or the United States Government