The high rate of obesity has become a growing problem in the modern world. Obesity is associated with the incidence of several comorbidities, such as cardiovascular diseases and type 2 diabetes. Despite weight loss being considered the most important remedy for obesity, long-term weight maintenance is also important.

Study: High Compared with Moderate Protein Intake Reduces Adaptive Thermogenesis and Induces a Negative Energy Balance during Long-term Weight-Loss Maintenance in Participants with Prediabetes in the Postobese State:A PREVIEW Study. Image Credit: margouillat photo / ShutterstockStudy: High Compared with Moderate Protein Intake Reduces Adaptive Thermogenesis and Induces a Negative Energy Balance during Long-term Weight-Loss Maintenance in Participants with Prediabetes in the Postobese State:A PREVIEW Study. Image Credit: margouillat photo / Shutterstock

Background
Metabolic adaptation, i.e., adaptive thermogenesis (AT), could be the key factor preventing long-term weight-loss maintenance. AT causes a decrease in energy expenditure, which is significantly more than the predictions based on reductions in fat mass (FM) or fat-free mass (FFM).

Energy expenditure adaptations have been found to last multiple years after a weight loss period. Therefore, after weight loss, a reduction in AT is extremely important for long-term weight loss maintenance. Some factors have been identified to reduce AT, such as physical activity, cold-induced brown adipose tissue activation, tea catechins, and capsaicinoids. Furthermore, high protein (HP) intake was also linked with AT reduction after weight loss.

Interestingly, an HP diet leads to enhanced FFM, resting energy expenditure (REE), diet-induced energy expenditure (DEE), and total energy expenditure (TEE). The combination of enhanced physical activity and an HP diet is able to preserve REE in spite of a reduction in FM and FFM. Compared to a low protein diet in individuals with stable weight, an HP diet for twelve weeks was seen to maintain the sleeping metabolic rate (SMR), TEE, and DEE. However, it is imperative to understand if the HP diet post-weight loss counteracts AT.

About the Study
A recent Journal of Nutrition study evaluated whether the HP diet could reduce AT and the expected positive energy balance (EB) during weight maintenance after weight loss in prediabetic patients in their post-obese phase. This research is a part of the prevention of diabetes through lifestyle intervention and population studies in Europe and around the World (PREVIEW) study.

The PREVIEW study is associated with three years of weight loss and weight maintenance intervention in four intervention groups. These groups differ in the dietary component, i.e., HP (low-glycemic index) and moderate-protein (MP) diet (modest glycemic index), and physical activity. This study aimed to understand the manifestation of type 2 diabetes after three years of interventions. In addition, the changes in body weight, insulin resistance, and body composition were analyzed.

The current study compared the effects of a controlled HP diet with an MP diet on EB and AT. This assessment was conducted after the completion of the PREVIEW study using a fully controlled respiratory chamber. A controlled HP diet was hypothesized to stabilize AT and elevate energy expenditure. 

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A total of 38 participants were recruited to analyze the impact of two diets (HP and MP), differing in protein/carbohydrate ratio, on energy expenditure and respiratory quotient (RQ). A total of 20 individuals (male-7, female-13), averaging 64 years of age, consumed the HP diet, and 18 individuals (male-9, female-9), averaging 65 years of age, consumed an MP diet. Fat-free mass and fat mass were used to calculate the predicted resting energy expenditure (REE).

Study Findings
The varied levels of macronutrient composition in the HP and MP diets resulted in the varied protein and carbohydrate balance between the two groups. In the HP group, protein intake and oxidation were higher, which caused a more positive protein balance compared to the MP group. However, compared to the MP group, the carbohydrate balance was less positive in the HP group due to lower carbohydrate intake and oxidation.

Interestingly, a lower fat balance was observed in the HP group with reference to the MP group. No significant difference in BMI, FFM, FM, energy intake, energy expenditure, or body-fat percentage was observed between the two groups. Based on energy expenditure, a 48-hour HP diet induced a negative EB and elevated REE, which were absent in the MP group.

Notably, the HP diet counteracted AT during weight maintenance after weight loss; however, the MP diet enhanced fat oxidation. In the HP group, a lower EB was found concerning MP, which was linked to reduced AT in the HP group. 

Consistent with previous studies, the current study revealed the presence of AT up to 34 months after an 8-week weight loss period. During this period, participants underwent a reduction of around 11.9% of their body weight. EB was positively correlated with RQ.

Conclusions
The current study revealed that compared to the MP diet, the HP diet led to a negative EB, which counteracted AT for around 34 months after weight loss in prediabetic individuals during the post-obese state. The study's finding emphasizes the importance of adherence to an increased protein/carbohydrate ratio diet for a prolonged period to maintain weight after weight loss.

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