The 10-Day Diet for Weight-Lifting Women

Aggressive Dieting vs. Optimal Calories

How much body fat can women lose in 10 days? Is muscle mass affected? Here’s everything you need to know.

Want to lose 3 pounds of fat in only ten days? There’s a diet and training plan for that. It’s even “science-based.”

But what if that same plan caused you to lose some muscle while impairing your thyroid function and metabolism? Still worth it? Probably not. Muscle loss paired with fat loss, accompanied by a drop-kick to the metabolism, usually leads to a smaller but flabbier body. And you’ll regain the fat anyway.

But there may be a way to fix this 10-day diet, losing the same amount of fat (or close to it) while retaining muscle, keeping your hormones healthy, and not buggering up your metabolism. First, let’s look at the original study on this aggressive plan, then we’ll make it better.

The 10-Day Study

Researchers recruited 30 weight-lifting women with a body fat percentage of 24% and divided them into two groups:

Group 1 – Optimal Calories

Based on the energy availability formula, this group consumed 2400 calories per day (50 kcals/kg FFM). This means they ate enough to maintain body weight and fuel their workouts. Their daily macro breakdown looked something like this:

Protein: 100 grams
Carbs: 310 grams
Fat: 80 grams

Group 2 – Low Calories

This group consumed 1350 calories per day (25 kcals/kg FFM) – a big 45% caloric deficit. Their daily macro breakdown looked like this:

Protein: 100 grams
Carbs: 145 grams
Fat: 40 grams

Both groups were supplied with food and put on a supervised weight training program: two upper and two lower-body days. They also did cardio on two of those days: one day of intense intervals and one easier, longer session. They took one off-day per 5-day cycle and went through the whole shebang twice.

The women underwent a lot of blood tests, DEXA scans, tests of resting metabolic rate, muscle protein synthesis testing, and quizzes to identify their love language. (I may have made one of those up.)

Get to the Good Part! What Happened?

Here’s what happened to each group after ten days:

Group 1 – Optimal Calories

  • Muscle Protein Synthesis: Increased. This indicates trending muscle gains.
  • Body Composition: Muscle mass increased by about 1 pound. Body fat decreased by just over 1 pound.
  • Resting Metabolic Rate: Slightly boosted (by 14 calories).
  • Thyroid Hormone: No change.

Group 2 – Low Calories

  • Muscle Protein Synthesis: Decreased. This indicates trending muscle loss.
  • Body Composition: Muscle mass decreased by about 1 pound. Body fat decreased by 3 pounds.
  • Resting Metabolic Rate: Impaired (by 65 calories).
  • Thyroid Hormone: Significantly decreased.

What Should We Make of This?

While the aggressively dieting group did lose two more pounds of fat than the other group, they also lost muscle and sucker-punched their metabolic rates and thyroids.

On the flip side, the maintenance-calorie group gained some muscle, didn’t throw a monkey wrench into their metabolic rate or thyroid health, and still managed to drop a little fat. (I’m guessing that even though these were experienced lifters, the supervised training was more challenging than their usual workouts, so they lost fat on what researchers thought were maintenance-level calories.)

Remember, all of this happened in just ten days. Extend this plan over a few months and the low-calorie group would be in a world of metabolic trouble. The optimal calorie group, however, would be hotter.

Can This Plan Be Improved?

A 10-day diet is appealing. Could we fix the problems and make it work? Well, if you’re determined to try it, here’s what T Nation contributor Bill Campbell, PhD., recommends:

  • Keep the strict 45% caloric deficit and training program.

  • Make it a 9-day diet. Diet for 4 days, then return to maintenance calories on the 5th day (a refeed, not a cheat day). Then, diet again for 4 days. Dr. Campbell says this will prevent muscle loss. This is basically like the plan outlined in my Non-Linear Diet for Lifters article.

  • Increase protein intake to 1 gram per pound of body weight. Reduce fats and carbs to make room for it. I recommend MD Protein (on Amazon) because it contains micellar casein, which stimulates metabolic rate while being anticatabolic.

Those changes should fix the drawbacks while still allowing for some pretty impressive results in a short amount of time. Just make sure you’re not prone to disordered eating tendencies. A 45% deficit is harsh. Don’t let it be the start of an unhealthy starve/binge pattern.

You could just be more patient and use a modest calorie reduction for longer, something like a 25% deficit, which isn’t going to screw up anything as long as you’re eating lots of protein and lifting weights.

The real take-home message? Women can lose fat, build muscle, and ultimately get the body they want by following the optimal calorie plan.


Note: Thanks to smart-guy Bill Campbell and his smart-guy newsletter, Body by Science, for pointing out this study.



  1. Oxfeldtr et al. “Low energy availability reduces myofibrillar and sarcoplasmic muscle protein synthesis in trained females,” J Physiol. 2023 Aug;601(16):3481-3497.

This is a great report-out. I find even women who know better, like my wife, still get stuck on a scale number. Breaking it down into tissue obviously tells a story, but I think showing the future impacts on metabolic rate and thyroid hormones is really powerful


For sure. I like studies like this that allow us to better see what’s really happening during a diet instead of relying on the least-informative instrument: the scale.

It would be fun to see this same kind of study, with all the scans, blood tests, etc., applied to something like Weight Watchers and other “normie” diets where most participants aren’t even lifters.


That would be cool. I’ve got to imagine we’d just see numerical benefits across the board from any group engaging in caloric restriction? If the control group is “do what you were doing,” that’s got to be the worst outcome in my speculative mind.

Yeah, in most weight loss studies, just about every deficit group gets results on basic things like weight lost and waist measurements. They often throw in a “don’t change anything” control group, but it’s not even necessary really. The real fun comes with blood tests, DEXA scans, metabolic rate testing, and follow-ups weeks, months, or even a year later.

I have a few more nutrition and fat-loss articles that really dig into some interesting studies. This one is wild: The Most Effective Diet You Should Never Do.

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Great article! More fuel for the V-Diet, which I need to revisit making a regular part of my lifestyle.

And you’re right, of course, everyone can absolutely be their own control in these interventions.

Anyway, I enjoy these but don’t press myself to go find the literature. I appreciate you making it so accessible.

Awesome, thanks! That’s the idea here: take a 30,000+ word, mind-numbingly boring study and break it down into real-people words with a take-home message. Dr. Bill Campbell helps too with his newsletter, Body by Science. I use that a lot because he always seems to find the most applicable studies. It’s a paid subscription, but worth it.


OK, but you need to specify age group, otherwise all this is useless (or misunderstood). Age, whether they have done dieting before, and overall hormonal status (are they on the pill?) are essential.

• Ages 18-30

• Not using hormonal contraceptives. Most good studies reject women on the pill since artificially wrecked hormones could throw off results.

• As women training 5 days a week and having an average of lower-20’s body fat, I think we can assume they had dieted before or knew a thing or two about nutrition.

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I would love for T-Nation to have more female writers write workout and nutrition articles for women. That would spare us the sexism in the selections quoted above.

Quote 1: That’s a jokey joke. I would’ve made the same one if the article had been about men. Let’s break it down. Study participants went through a ridiculous number of tests. I’m surprised they didn’t test for other things, like (joke forming… what would be a silly thing to test in a study like this? Hmmm…) love languages! Get it? Love languages! Chortle! Nevermind.

Quote 2: The optimal calorie group would be hotter. So would men if they lost fat and built more muscle. I bet even non-binary people who identify as cats would be hotter. We can’t say that fitter women are hotter now?

Quote 3: I love this one, mainly because those lines weren’t in the rough draft. The female senior editor of T Nation strongly suggested I add them. These sexist women, amiright?

Kinda weird being called sexist since I’ve written dozens of articles on a traditionally male website that are all about helping women achieve their fitness goals… which, by the way, draws the ire of some dickish men (“What is this?! E-Nation?!”)

I think maybe, just maybe, you’re always on the lookout for sexism, which means you’ll always find it, even where it doesn’t exist.


That is good to know. I’m glad. You may want to add a disclaimer that the article was proofread and edited by a female colleague in the future.

Kinda weird, I didn’t say that you were sexist. The writing was. Having read T-Mag/Nation for maybe 25 years now, have always appreciated that there are many articles here for women. Keep up the good work.

Sorry Chris, I called it as I saw it for this specific article. Thank you for the reply and for being open to feedback. I look forward to many more good articles from you and your colleagues.