Under-eating may sound good in theory as a way to fast track your results. However, extreme dieting is unsustainable and rarely produces lasting results.
Why do we recommend hitting your macro targets instead of trying to eat less? This mainly comes down to how our bodies react to under-eating.
Fortunately for us, the human metabolism is incredibly robust. It adapts to a wide range of conditions, including the ability to withstand periods of famine.
Sadly, this isn't the kind of news one would like to hear when attempting weight loss. As we restrict calories and have less body fat, our metabolism adapts by becoming more efficient at its processes to conserve energy.
The more we try to speed up weight loss through under-eating, the more the body adapts. Eventually, we lose weight. However, it's not always as much as we would expect, given how low calories we are eating. This is due to those adaptive processes.
Why isn't this favorable? Under-eating can have several consequences.
It can unnecessarily speed up the rate of metabolic adaptation
It may put you at greater risks for losing lean mass (muscle), not fat
It can increase negative symptoms of dieting such as:
Hunger and appetite
Low mood and irritability
Increase risk of overeating or binge eating
If you can't eat to the prescribed targets, you can increase your rate of loss in the coach settings. This will reduce your macro targets since it will be a more aggressive goal.