Nutrition
Why an extreme calorie deficit is not an obvious weight-loss strategy
Short answer
Losing weight generally requires an energy deficit, but bigger is not automatically better. Too low an intake can make nutrition, training and recovery harder to sustain.
Your body needs more than just weight loss
When too little energy is left for bodily functions over a long period after accounting for training load, problematic low energy availability can develop. In athletes, this can be linked to disruptions in hormones, bone health and performance, among other things. The IOC describes this under REDs. Not every calorie deficit is REDs, and an online calculation does not make that diagnosis. [1]
Your metabolism does not switch 'off'
During weight loss your energy expenditure changes; a lighter body generally needs less energy. That does not mean eating little makes fat loss impossible. It can, however, explain why an earlier approach later produces less weight loss. [2]
When are very low-energy diets used?
NICE describes specific uses under professional supervision. Such programmes have conditions, support and a limited duration. This is no argument for eating as little as possible on your own. [3]
In practice
Choose an approach that leaves room for balanced nutrition, and also assess how you function and recover. Discuss persistent dizziness, missed periods, severe fatigue or eating problems with a doctor or dietitian. Do not blindly cut further because the scales have not moved for a few days.
