Do You Have to Keep Eating Fat on Keto? No. Fat Is the Optional Macro (2017 Reply)

2017-07-29

In this recording

A two-and-a-half-minute video reply from July 2017. A group member asked whether they had to keep eating fat. I promised to tag them in a longer post with example macros. It was never posted to YouTube.

[0:00] Short answer: no, you don't need to keep eating the fat. Fat is optional. I quoted a forum motto: if you're already high fat, all you need is low carb.
[0:00] Protein is needed so you don't lose muscle, especially if you work out. Protein needs are fairly fixed, tied to lean mass, height and sex rather than how much fat you carry.
[0:00] A 5'7" woman and a 5'10" woman don't need very different protein. Even at the extremes it's maybe 10 or 20 g either side of a basic 80 g.
[0:58] For most women I suggested 80 g protein, 20 g carbs, and the rest fat, but only as much as you need.
[0:58] I said I don't want anyone starving, and I don't think eating under 500 calories a day for long is healthy. I mentioned the Minnesota starvation experiment as what real starvation looks like.
[0:58] I said something like 1,000 to 1,100 calories is a fairly significant weight-loss deficit for most women, and the shortfall comes out of your body fat.
[0:58] When fat drops, your macro percentages change. The people who insist on "70% fat, 20% protein, 5% carbs" are wrong.
[1:54] 80 g protein, 20 g carbs and only 40 g of fat would be fine. It would shift the pie chart, and people would call it high protein. It isn't. The protein and carb grams haven't changed.
[1:54] If you're hungry, use fat to feel full. If you're not hungry, stop eating fat. You have fat on your body. Stay hydrated, get your protein, limit your carbs.

Watching this in 2026

This is an idea I repeated constantly, here in under three minutes: carbs and protein are fixed, fat is the dial. I'd teach it the same way today, in grams, not percentages. Percentages are a ratio, and a ratio changes every time you eat less of one thing. That's why someone who cuts fat suddenly gets told they're "high protein" by people looking at a pie chart.

Where I'd be more careful is the calories. I offered 1,000–1,100 a day as a typical deficit for women in a reply to someone I didn't know. That's low for many people, especially taller or active women, and I'd rather someone eat to the end of their hunger than aim at a number. Eleven days earlier I told a hungry member not to cut calories at all in the first two weeks (video AQKD1882). That's the better advice for a beginner. I also cited the Minnesota starvation experiment without giving the source, and it isn't on the evidence pages I use, so I've left its numbers out.

Checking the protein number

My 80 g for most women lines up reasonably with the literature for someone losing weight:

The adult RDA is 0.80 g/kg a day (National Academies, 2005). For a 70 kg woman that's 56 g. That's a floor, not a weight-loss target.
Leidy et al. (2015) associated about 1.2–1.6 g/kg a day with better appetite control and weight management. For the same woman that's about 84–112 g.

So 80 g is above the floor and a little under the range in that review. It's a sensible starting point, and the "+20 if tall, +20 if training" modifiers I added later move it into that range (video UygKGoP_BtA).

Who should talk to a doctor

If you have kidney disease, set protein with your doctor. If you take diabetes or blood pressure medication, tell your doctor before cutting carbs. If you have a history of an eating disorder, don't use a calorie number from a video at all. Work with your doctor or therapist.

Key points

Carbs and protein stay fixed. Fat is optional and is what you raise or lower.
Count in grams. Percentages shift when you eat less fat, and that's fine.
Eat fat for fullness when you're hungry, and skip it when you're not.
80 g protein is a reasonable base for most women, more if tall or active.
Don't chase a very low calorie number. Let appetite set the deficit.