Health In Focus
  • Following intentional weight loss, many persons find it difficult to maintain the new weight despite restricting total calorie intake, and the reasons for this are not entirely clear
  • One hypothesis put forward termed the “carbohydrate-insulin model “(CIM) of obesity”, which states that consumption of a diet high in carbohydrates results in hormonal changes in the body that promote weight gain
  • Current randomized study compares the efficacy of a low carbohydrate in promoting expenditure and weight loss compared to a high carbohydrate diet

Consumption of a diet high in carbohydrates results in metabolic changes in the body that promotes weight gain even if a person reduces overall calorie intake, according to a multicenter randomized conducted across two cities in the US.

The findings of the study appear in the BMJ titled "Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial".

Testing the Carbohydrate Insulin Model of Obesity

Consuming a diet rich in carbohydrate results in a physiological state marked by hunger pangs and food craving, deposition of fat and decreased burning of calories, leading to weight gain, especially in persons who have increased basal insulin secretion, according to the carbohydrate insulin model (CIM) of obesity.
How to Maintain Your Weight After Initial Weight Loss

Until now, the model was not widely accepted due to the lack of evidence from controlled feeding studies. The current randomized controlled feeding study was therefore undertaken to try and establish the veracity of the carbohydrate insulin model for obesity.

Design of Study

  • This randomized controlled study included 164 participants aged between 18 to 65 years with a body mass index of 25 or more and body weight not exceeding 160 kilos
  • For the study, the participants were randomly assigned to three different diet groups comprising high amounts (60%) carbohydrate in 54 persons, moderate amounts (40%) in 53 persons, or low amounts (20%) in 57 persons.
  • The relative amounts of added sugar, saturated fat and common salt was common to all groups
  • After 20 weeks of follow-up with controlled feeding, the energy expenditure in the different diet groups were assessed

Role of Carbohydrate Diet in Promoting Weight Loss

  • During the study, total physical activity, resting energy expenditure, and moderate to high-intensity physical activity were slightly higher in the low carbohydrate diet group
  • Time spent in inactivity and skeletal muscle work efficiency was identical in all groups
  • For every 10 percent reduction in carbohydrate to total calorie intake, there was an increase in energy expenditure of 50 to 70 kcal/d or a difference of 209 to 278 kcal/d in the total energy expenditure
  • The difference in total energy expenditure between the low and high carbohydrate diet groups with higher levels of insulin secretion was more than double the difference in total energy expenditure in participants with low insulin levels. This suggests a subgroup of persons who may particularly benefit by carbohydrate restriction
  • Levels of the hormones Ghrelin and leptin are known to cause weight gain declined more in the low carbohydrate diet group compared to the high carbohydrate diet group. The decline in Ghrelin was steeper compared to leptin
  • The energy intake or total calorie consumption in participants assigned to the high, moderate, and low carbohydrate test diets, altered on an average during the course of the study by 139 kcal/d (−4 to 282), 175 kcal/d (42 to 308), and 269 kcal/d (143 to 396), respectively and the differences were higher in participants with higher insulin levels
Thus, the findings of this controlled feeding trial over 20 weeks suggest that total energy expenditure with consequent weight loss was significantly more in persons assigned to a low carbohydrate diet compared to those assigned to a high carbohydrate diet of similar protein content, irrespective of initial body weight.

According to the authors, if weight loss or energy expenditure in persons with low carbohydrate diet were to continue, this translates into a 10-kilo weight loss in a typical 30-year-old man weighing 100 kilos with a height of 178 cm, assuming calorie intake remains same.

Factors Found to affect Weight Loss Attempts

  • Pre-weight loss insulin levels - Persons with high pre-weight loss insulin levels showed the greatest levels of energy expenditure in the study
  • Genetic factors - Persons with a genetic predisposition to obesity have a higher risk of weight gain and obesity on consuming high carbohydrate load sugary drinks compared to non-consumers

Further Research Plans

  • To assess the effect of carbohydrate restriction on body weight along with reduced total calorie intake
  • Comparison of low-fat diet (without altering carbohydrate amount) to diet restricted in carbohydrate in decreasing glycemic index
  • To determine specific variations in outcome related to insulin levels and other factors
  • Evaluation whether extreme carbohydrate restriction (ketogenic diet) offers added benefit to obesity and diabetic patients
  • Finding the mechanisms by which dietary composition affects energy expenditure


Despite potential limitations, the study suggests the benefit of reducing carbohydrate quantity in diet in promoting weight loss even if total calorie intake is not reduced. The findings of the study could help in more effective obesity and weight management measures and incorporation into weight management routines

Reference :
  1. Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial - (

Source: Medindia

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