Last update and review: May 11, 2020.
We have been reviewing the published literature on the topic of long-term caloric restriction and its impact on metabolism and behavior. Our focus is mostly on how to restore a normal metabolic and hormonal profile in individuals who, intentionally or unintentionally, entered a state of prolonged caloric restriction due to excessive exercise or a restrictive diet.
There were a couple of studies that came to our attention (1), (2). They described the weight loss and metabolic profile changes in a randomized controlled trial (RCT) where caloric restriction was used as the main tool.
The subjects were a group of young, overweight (BMI 36), healthy (TG<100mg/dL) adults.
There were two groups, one with 60% carbs and the other with 40% carbs in the diet. The caloric restriction was 30% and then 10%, which were calculated based on the baseline caloric intake of roughly 2750 kCal a day.
The subjects lost the same weight and felt similarly on 30% and on 10% CR. Their metabolic markers improved. However, insulin levels improved from around 11mIU/L to around 8mIU/L only. This is above the optimal level.
The subjects on the diet with higher carbs (60% of the caloric intake) were somewhat more stressed by the reduction in calories than the subjects on lower (40% of the caloric intake).
The good outcome was that there was no profound reduction in the metabolic rate of the subjects.
The verdict.
The diets were hardly optimally designed for weight loss. Still, the subjects lost 8% of their body mass by the end of the 12-month study period.
The interest of this study is limited for our purposes. Indeed, we do not get a lot of information on how to avoid and how to repair a deterioration of hormonal and behavioral profile observed in prolonged caloric restriction. Especially in the cases of low carb diets.
If you need help with the design of your own weight-loss program, with a review of your hormone profile and other biomarkers, do not hesitate to get in contact with us.
Below, there some details on the studies mentioned in this article.
Physically active were excluded (2):
Additional exclusion criteria included a high level of physical activity (>12 hrs/wk)
Each subject was then randomized to receive an HG or LG diet and one of two levels of CR (10% or 30% relative to baseline energy requirements). By design, 34 subjects were randomized to the 30% CR groups and 12 subjects to the 10% CR groups
Interestingly, the subjects on 10% caloric restriction (CR) and 30% CR lost a similar amount of weight (2):
Both the 10% and 30% CR groups consumed significantly less energy during CR than at baseline (p<0.01) and lost similar amounts of weight.
The tables below are from the study by Das, 2007 (1). They provide details on the studies’ design and outcomes.
