Minimum time for diet and max % loss per week

Hi there, 2 related questions:

  1. Is there a minimum amount of time to be on a diet before you can say fat loss has occurred? My understanding is that initially, the lost weight is primarily glycogen or water. Assuming in starting from around 20-23% body fat.

  2. I know the optimal % bodyweight to lose is a max of 1%/week if you want to preserve muscle mass. But I’ve come to the realization that I’d rather be lean quickly, even if it means losing muscle in the short term. How much more than 1%\week can I try to lose if I primarily care about fat loss and am willing to lose more muscle than if I were losing at an optimal rate? Is 2% body weight per week ok, as long as I can maintain successfully afterwards?

I think there are a few underlying assumptions that, while widely believed, are not well-supported:

  1. 1% BW loss per week is not optimal. It’s just a rule of thumb given by some, but it’s not based on anything.
  2. Muscle loss during weight loss for those who are training and eating enough protein is pretty minimal, in general.
  3. The 75/25 “rule” of weight loss suggests that 75% of all weight lost is typically fat and 25% is lean body mass (e.g. everything that is not fat). This was made up and not supported by evidence. To your questions:
  1. Fat loss can be measured in as short a time period as a few hours with some sophisticated equipment. Fat loss happens during the first phase of weight loss too. I can’t tell you how much fat vs how much water is being lost in the first week or so, but phase 1 is usually over within 5-10 days.

  2. The rate of weight loss is decided by the energy deficit. The greater it is, the greater the weight loss. Whether or not this turns into an “optimal” body composition depends on other factors. I’d favor loss of up to 5% starting BW per month for individuals without obesity.