Energy balance
Prolonged calorie restriction (25% deficit) in nonobese overweight adults induces metabolic adaptation, reducing 24-hour energy expenditure by ~6% more than expected from the loss of fat-free mass alone.
If you restrict calories for 6 months, your body will burn fewer calories than expected for your new size. This is a normal survival mechanism, not a failure. To manage this, you may need to adjust your calorie targets or increase activity as you lose weight, rather than assuming your old maintenance calories will still apply.
After adjustment for changes in body composition, sedentary 24-hour energy expenditure was unchanged in controls, but decreased in the calorie restriction (-135 kcal/d [42 kcal/d]), calorie restriction with exercise (-117 kcal/d [52 kcal/d]), and very low-calorie diet (-125 kcal/d [35 kcal/d]) groups (all P<.008). These 'metabolic adaptations' (~6% more than expected based on loss of metabolic mass) were statistically different from controls (P<.05).
Why this rating
Randomized controlled trial, blinded assessment, rigorous metabolic chamber measurements, large sample relative to metabolic studies.
Source
Effect of 6-Month Calorie Restriction on Biomarkers of Longevity, Metabolic Adaptation, and Oxidative Stress in Overweight Individuals
Leonie K. Heilbronn et al. · JAMA · 2006
DOI 10.1001/jama.295.13.1539
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