Some Musings About Differential Energy Metabolism With Ketogenic Diets

Abstract

Ketogenic states are of 3 major types: total starvation and those resulting from the consumption of semistarvation, ketogenic diets, and eucaloric ketogenic diets. All are characterized by little or no dietary carbohydrate, resulting in a fat‐based metabolism with sustained ketonemia of varying degrees in each state. The latter 2 diets are clinically useful with important impacts on both aspects of the energy balance equation with increased satiety and less hunger on the intake side and probably increased energy expenditure on the output side; both may have important implications for the successful long‐term management of obesity. Consideration of older research regarding the hormonal response to carbohydrate‐free dieting and recent findings on hepatic glycogen status that occurs with sustained ketonemia support the likelihood that there are profound differences in 24‐hour gluconeogenesis rates between ketogenic diets and balanced diets containing substantial carbohydrate. This metabolic distinction could have a meaningful impact to increase the thermic effect of feeding and daily energy expenditure amounting to 100 kcal/d or more with each of the ketogenic diets.

Energy Requirement Is Higher During Weight-Loss Maintenance in Adults Consuming a Low- Compared with High-Carbohydrate Diet

“…The components of energy expenditure accounting for the higher observed energy requirement remain speculative and warrant further research but may include resting energy expenditure ( 17 ), spontaneous physical activity ( 18 ) (both of which were marginally higher on the low-carbohydrate diet in our study as previously reported [ 8 ]), sleeping energy expenditure ( 19 ), nutrient cycling ( 20 ), and better access to metabolic fuels in the late postprandial state ( 21 ). Hormonal changes accompanying a low-carbohydrate diet may mediate, to some degree, several of these components.…”

Energy expenditure and body composition changes after an isocaloric ketogenic diet in overweight and obese men: A secondary analysis of energy expenditure and physical activity

“…The higher value is suspect, having been based on a theoretical estimate [15] of a 400–600 kcal/d expenditure to support gluconeogenesis under conditions very different than those in the Hall et al study, specifically prior to adaptation to a low-carbohydrate diet with only endogenous, not dietary, protein as the substrate. In contrast, Bistrian [16] recently estimated the energy cost of gluconeogenesis associated with consumption of a ketogenic diet at 110 kcal/day (not allowing for tissue glucose demands) under conditions very similar to those employed in Hall et al (i.e., eucaloric after an adaptation period). The lower value cited by Hall et al’s (300 kcal/d) was based on the results of a randomized cross-over study by Ebbeling et al [17] in which EE DLW in free-living weight-reduced subjects was, depending on how expenditures were calculated, ~250–325 kcal/d greater when subjects ate a low-carbohydrate/high-fat diet compared with a high-carbohydrate/low-fat diet.…”

“…This observation argues against a change in muscle work efficiency in the KD period; however, it is not known whether the efficiency of muscle work associated with the increase in other forms physical activity in a ward setting may have been affected. Greater physical activity outside the chambers may also have increased EE during the KD period by creating a demand for glucose, some of which under the condition of severe dietary carbohydrate restriction would be met through the energetically expensive process of hepatic gluconeogenesis (see also [16]). The elevated plasma concentrations of glucagon and the increase in protein catabolism (as evidenced by increased urinary nitrogen, urea and ammonia excretion) during the KD period in the Hall et al study [8] (see also [28]) are consistent with such a higher rate of gluconeogenesis, which has been suggested as a contributing cause of the increased thermogenesis associated with consumption of ketogenic diets [16].…”

Macronutrient Proportions and Fat Type Impact Ketogenicity and Shape the Circulating Lipidome in Dogs

“…In humans undergoing weight maintenance, low carbohydrate foods also increase the requirement for dietary energy [51], and a rodent model has documented the physiological underpinnings of the effect [52]. Mechanisms relevant to dogs have been proposed whereby this might occur [53], and a biological framework has been proposed that invokes hormonal control of energy balance [54,55]. Whether there is indeed increased energy expenditure when consuming low carbohydrate foods is controversial [56][57][58][59][60][61][62][63][64].…”