Effects of a low carbohydrate diet on energy expenditure during weight loss maintenance: randomized trial

Why Your Body Might Burn More Calories on a Low-Carb Diet

You might wonder why weight loss is often followed by frustrating weight regain. Many researchers believe the body's metabolism slows down drastically after dieting, making maintenance a constant battle. This landmark study, published in the BMJ in 2018, investigated whether the type of calories you eat—specifically the ratio of carbs to fat—can actually influence how many calories your body burns at rest.

The Core Evidence: Boosting Metabolism During Maintenance

This research focused on 164 adults who successfully lost about 12% of their body weight first. They were then split into three groups for 20 weeks of weight maintenance, eating diets that were high (60%), moderate (40%), or low (20%) in carbohydrates. Protein intake was kept the same across all groups.

The findings challenge the simple idea that "a calorie is a calorie":

1. Low Carb Increases Energy Expenditure (Calories Burned)

The study found that total energy expenditure (TEE)—the total number of calories the body burns each day—differed significantly across the diets.

• For every 10% decrease in the carbohydrate contribution to the diet, participants burned an average of 52 additional calories per day.
• Compared to the high-carbohydrate group, those on the low-carbohydrate diet burned significantly more calories: 209 calories per day more in the overall analysis.
• Think about it this way: Maintaining weight on a low-carb diet meant the body was running "hotter," burning the energy equivalent of a modest daily workout without any extra physical activity.

2. The Insulin Connection (The Biggest Boost)

The research found that the effect of the low-carb diet was most pronounced in individuals who had high insulin secretion before they started losing weight (common in Type 2 diabetes).

• In this group of participants—who are often those most susceptible to metabolic issues and weight regain—the low-carbohydrate diet caused their bodies to burn an astonishing up to 478 calories more per day than the high-carb group.
• This massive metabolic advantage is consistent with the carbohydrate-insulin model, which suggests that reducing carbohydrate intake stabilizes insulin levels, thereby increasing the body’s ability to burn fat (energy) rather than storing it.

3. Hunger Hormone Reduction

The study also looked at hormones controlling appetite:

• Levels of Ghrelin, often called the "hunger hormone," were significantly lower in participants on the low-carbohydrate diet compared to the high-carbohydrate diet.
• Leptin (the satiety hormone) was also significantly lower in the low-carb group (in the per protocol analysis).

Practical Application and Relevance for People with Diabetes

The finding that the greatest metabolic benefit (burning up to 478 extra calories per day) occurs in those with high insulin secretion has direct and significant relevance for people suffering from Type 2 diabetes and related metabolic issues.

Note: This is an exploration of the research, not medical advice. Always consult your healthcare provider before making significant changes to your diet, especially if you are managing diabetes medications.

1. Fighting the Metabolic Slowdown: If you have struggled with weight regain after dieting, this research suggests that reducing carbohydrates may be a key tool for keeping your metabolism active during the crucial weight maintenance phase. Discuss with your doctor whether shifting your macronutrient ratio could help maintain long-term results.
2. A Powerful Tool for Insulin Resistance: Since high insulin secretion is a hallmark of insulin resistance (common in Type 2 diabetes), this study indicates that lowering carbs may be the most metabolically beneficial strategy for those with the most sensitive insulin systems. You might consider this approach as a targeted way to support your body's energy regulation.
3. Managing Hunger Naturally: The reduction in the hunger hormone Ghrelin suggests that a low-carbohydrate diet might make weight maintenance psychologically easier by naturally suppressing appetite. If constant hunger undermines your efforts, this specific dietary change might offer a solution.
4. Prioritizing Diet Composition: The study showed that diet composition affects energy expenditure even when calories and protein are controlled. This empowers you to think critically about the type of food you eat, not just the amount, to support long-term metabolic health.