Dear Mark: OMAD for Women, Low-Carb Glucose Testing, and Carb Limit When Fasting

For today’s edition of Dear Mark, I’m answering three questions taken from last week’s post on the power of pairing low-carb with fasting. First, do I have any advice for a woman who’s struggling to see results eating one meal a day? Second, how does low-carb interact with the different types of glucose tests you can take? And third, what are my thoughts on carb limits when fasting? Is lower always better? Is there a carb threshold after which fasting stops working so well?

Let’s go:

I have been dappling in low carb for nearly year and in the last 2-3 months I have been playing around with OMAD. My question is, I eat ’till I’m full ,which is about 12-18 grams of carbs, never over 100g protein and around 100g fat, sitting at 1000-1400 calories—but I’m not losing weight. Over 3 months I’ve lost about 6kg and I have about 30kg to lose. Do I keep going? I’m enjoying it but I get frustrated about the lack of weight loss (I’ve lost a dress size).

The majority of women don’t do well on one meal a day. Consider the average office worker struggling to lose weight. They do coffee for breakfast and maybe have a salad with no meat (and few calories) for lunch, struggle mightily not to eat five stale donuts at 3p.m. in the break room, only to cave at night and eat a sack of potato chips and take out while streaming some show.

My point is not that these people would do better if only they ate a solid meal for dinner rather than chips and snacks and Netflix. Nor is it that this problem only afflicts women and never men. Plenty of men do it, too, and have bad results. But it shows more quickly in women, who by nature of their reproductive physiology are simply more vulnerable to nutritional insults than men—on average. I explain the reasons this happens in this post on fasting for women. Long story short, because reproduction is far more costly and demanding on a woman’s body than a man’s (conception, pregnancy, nursing); woman are more finely attuned to caloric restriction and fasting. My point is that fasting for most of the day, every day, doesn’t work well for most women—it becomes a constant stressor, driving unhealthy cravings to which you eventually succumb.

It sounds like OMAD might not be working for you. Just one dress size (which is a better barometer than weight) in 3 months? Yeah, it might be time to try something else.

Was low carb with more frequent meals working?

I’ve seen a lot of men burn out on OMAD, too. Throw in some sleep disturbances, a heavy training schedule, work-related stress, cooking for the family, bills, and whatever other stressors modern life throws our way, and OMAD can be counterproductive.

For one thing, your calorie intake is way too low. One thousand calories is way too low; 1400 calories is really pushing it. Perpetually starving yourself for 22 hours a day and then trying to cram a big meal in that doesn’t even provide enough calories or nutrients just doesn’t work for most people. I can imagine your leptin is low, your caloric expenditure dampened, your thyroid function inhibited.

Here’s what you might try.

Do OMAD with 1000-1400 calories once a week. Twice max. Eat normal—two to three meals—the rest of the days. This way you pulse your fasting and OMAD’ing. You eat normal amounts of calories for five days a week and then drop them down low twice a week, giving your body a message of relative abundance punctuated with short bouts of scarcity.

I think that’ll work better for you. Write back with your results.

If you are low carb and need to do a glucose blood test and an A1C test: What is the best fasting times then? Just the night before or for 24 hours?

If you fast longer, shouldn’t the glucose reading be lower?

It really depends on what kind of test you take.

If you’re doing a fasting blood glucose test, fasting will probably lower it.

If you’re doing a postprandial blood glucose test, fasting will probably raise it. You’re asking your body to suddenly go from burning fat to processing 75 grams of pure glucose. The fat-based metabolism triggers transient insulin resistance, which inhibits your ability to process the glucose efficiently. Your postprandial reading will thus be higher than is “real.”

If you’re doing an HbA1c test, fasting won’t affect it. HbA1c is the “average” blood sugar over three months or so; a single meal will have no impact.

I totally agree with the science of this relationship. Mark, at what intake level of carbs are you considering this relationship no longer synergistic? Anything over 100 grams or should the carb intake be kept lower to have the greatest fat-burning / weight-loss effect?

The bulk of the synergy lies in the ease with which you can maintain the fast. Low-carb/fat-based metabolisms simply make it easier to slip into and remain in the fat-based metabolism of the fasting state. If you can easily fast, easily slip back into ketosis and maintain the fast while eating an otherwise moderate or high-carb diet, have at it. That isn’t as common as the opposite, drawing on my experience talking to hundreds of people about this.

However, some people get the best weight-loss effect by combining intermittent fasting, heavy weight training, and periodic/timed carb feeds. The trick is to time your carbs around your workouts, and eat no more than you’ve actually expended through glycogen depletion. That means you’re still in a fat-based metabolism because the carbs you do eat are going toward glycogen repletion rather than being burned for energy, so they never actually inhibit the burning of body fat.

If you’re doing CrossFit WODs that hit every muscle and leave you panting on the ground (or the equivalent), you could probably get away with 100-200 grams right after without any issues. It really depends, of course. More muscle, larger glycogen sinks. Some people just slip right back into ketosis more easily. Others have a life history that may inhibit this. But that 100-ish carbs after a “hard” training session that you feel should be a good target for most people.

You should keep fat low and protein high in these carb-heavy meals. What you want is to refill that glycogen and hit the protein hard.

That’s it for today, folks. Take care. Be sure to ask any followups or additional questions down below. Thanks for reading!

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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9 thoughts on “Dear Mark: OMAD for Women, Low-Carb Glucose Testing, and Carb Limit When Fasting”

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  1. Nodding my head at fasting not working well for some women, thank you for reiterating this point once again Mark.

    I get crazy hunger signals the following week if I fast for too long, I’m not overweight (under in fact) and fasting is never by choice, but even when I skip a meal or when things get really hectic two I don’t always immediately notice but the after effect last days and I don’t feel my best. I’m low to moderate carb too, but still doesn’t feel great for me.

  2. You said “postprandial blood glucose test” when I think you meant “oral glucose tolerance test”.

  3. I have read that n-acetyl cysteine is very beneficial (especially if you are getting sick), but when taken with glycine, reduces the benefits. Also, when combined with antioxidants, reduces those benefits as well. Are there some simple rules we can follow in regards to combining supplements?

  4. Dr. Fung suggests every other day for best weight loss. 24 or 36 hour fasts and eating 3 meals a day on feast days.

  5. I fast most days following a fairly early dinner until around 11a.m. or noon the next day. I’ve never seen any reason to fast longer than that. Two nutritious meals a day without snacking works well for me. OMAD would not.

    As a woman, I prefer Primal over keto (or OMAD and various other lengthy fasts) because Primal (Paleo) is a moderate approach that’s stress-free and almost effortless. I mean, who can’t do 80/20 or 90/10? It’s easy! Sometimes I go for days in what Mark calls “the keto zone”, but I never feel locked into it. I have zero interest in tracking grams of carbs, protein, etc. That equates to turning one’s food into a hobby, and I don’t think it should be.

    Our bodies don’t need to eat nearly as much or as often as our minds like to think they do, but there is a cutoff point that varies since we aren’t all alike. IMO, the real secret is mindful eating; i.e. to eat only when you’re actually hungry–not because you mentally or emotionally feel like munching–and to know which foods/ingredients to mostly avoid.

  6. A female co-worker of mine (in another building) who has gotten good results with intermittent fasting (IF), but still eats “normally” when not fasting, typically eats two meals a day during the week and then usually only one meal a day on weekends. As she explained it, it too hard to fast when everyone is coming in with lunch and at night when she cooks for her husband. On weekends, her husband fends for himself for breakfast and lunch, just as he does when she’s at work.

    My dabbling with IF has been unintentional and sporadic, so I haven’t bothered to track my results with it. Sometimes on weekends, I will eat a very late (as in early afternoon) breakfast of bacon and eggs and not be hungry the rest of the day, so I don’t. Other days, I’ll do the very late breakfast and be peckish in the evening, so I’ll eat a light meal. Other days, I’m flat out hungry, so I eat.

  7. I don’t like the idea of OMAD at all. Fasting is when you have negligible calories for at least 24 hours in my book. Fasting helps me with liver pain which thankfully is now only occasional. I have to be thankful for small favors… at least my liver tells me when it’s overworked.

    And a 24 hour fast is followed by at least 24 hours, preferably 3 days of normal eating.

    I’ve planned longer fasts and they’ve helped too. But I always spend a week or more getting back to normal eating afterward. Once a person’s body switches entirely to keto, there are no more cravings unless you eat something with calories. Even fat.

    Well, not for a couple of weeks anyway. I’ve lasted about 15 days with water only. When you get real hunger you don’t reach for chips and take out. That’s a stressed metabolism talking. Give the fast time to switch your body to keto (24-48 hours) and feel the magic of being craving free for several days.

    Do not try that during a period though. Won’t work, will make you feel like a 10 ton safe fell on you. Start the day after it’s gone.