Stalls are frustrating. You’re cruising along on your Primal or Primal + keto diet, and then wham—you hit a wall. It’s all a totally normal and expected part of the weight loss process. Weight loss is never linear. There are always downs, ups, and flat spots.
In fact, if you’ve been losing weight for a while, and then you stall out for a week or two, I wouldn’t even consider that a plateau necessarily. Your body might keep losing weight on its own if you give it time and don’t stress about it. Still, I get it, you’re eager to kick-start the weight loss again.
One strategy that gets tossed around is trying a carb refeed or “carb up.” Carb refeeds are touted as plateau busters and also, more generally, as a strategy to support weight loss. In today’s post, I’ll explain the logic behind this idea and explain why it might be effective, especially for women following a generally low-carb approach.
Let’s get some terminology out of the way. Strategically adding carbs to a low-carb diet is variously called a “carb refeed,” “carb up,” or “carb cycle.” These terms don’t have standardized definitions. In general, carb cycling usually refers to eating low carb for a certain number of days, then higher carb for a certain number of days, and repeating.
“Carb refeed” and “carb up” can mean the same thing, or they can mean adding carbs more intuitively when you feel like you need them.
Carb cycling strategies have long been used to promote leanness, especially by physique and other athletes trying to achieve low body fat percentages. In this context, carb cycling involves specific protocols, usually 5-6 days of very low carb eating combined with 1-2 days of higher carb eating. They may include exercise and fasting regimens, too.
The carb cycling protocols used for getting super lean aren’t the same as what we’ll be talking about for general weight loss and breaking out of a stall. For one thing, they usually involve more carbs than you probably need. We’ll get to that later. Also, although some of the mechanisms are probably the same, they focus specifically on depleting and refilling glycogen stores. For our purposes, that’s not so important.
How Do Carb Refeeds Work?
First let me say that the evidence for carb cycling strategies, especially with regard to weight loss and plateaus, is mostly anecdotal. There is pretty good data to support the pieces, but the whole picture has not been rigorously tested.
So what do we think is happening? There are a few (not mutually exclusive) hypotheses here:
Carb refeeds work by boosting leptin
Carb refeeds work by relieving the stress of dieting
Dieting is hard, and carb refeeds help us stick to them
Carb Refeeds Work by Boosting Leptin
Leptin is sometimes called the “satiation hormone,” but it’s probably more accurate to think of it as a starvation sensor.1 Its main role is to tell the brain whether we have sufficient energy on board, either in fat cells, which secrete leptin, or because we have recently eaten (especially carbs).
It’s well established that leptin levels drop both when we lose body fat and when we eat in a caloric deficit2 for even a short period. Remember, from an evolutionary perspective, weight loss signals that we are in a time of food insecurity and stress. Low leptin signals to the hypothalamus that we might be facing an energy shortage. In turn, the hypothalamus kicks on the processes collectively known as adaptive thermogenesis,3 or energy conservation. These include down-regulating thyroid activity and slowing metabolic rate, decreasing energy expenditure, and increasing hunger and appetite.
Premenopausal women’s bodies are especially sensitive to anything that sets off the “Danger! Starvation possible!” alarms. (Postmenopausal women are generally more resilient.) Leptin is a key player in that system. It is also involved in the regulation of insulin sensitivity and glucose metabolism, the female reproductive and immune systems, and skeletal and cardiovascular health. Basically, leptin is really important if we want to feel good and achieve optimal hormonal balance.
Leptin levels rise in response to eating carbohydrates specifically.4 Thus, one rationale behind carb refeeds is that by boosting leptin, we can reset the system. Basically, it tells the brain, “Hey, it’s cool, we have food around. It’s safe to let go of some of this body fat.”
Carb Refeeds Work by Relieving the Stress of Dieting
A related hypothesis is that dieting is physiologically stressful on the body. After periods of energy restriction, we see a decrease in thyroid hormones and an increase in cortisol (which may be related to falling leptin). These are part of the adaptive response that aims to restore energy balance. Carb refeeds alleviate the stress of being in a constant state of energy restriction.
Dieting Is Hard, and Carb Refeeds Help Us Stick to Them
One of the main reasons dieting hard is because of hormonal changes (ahem, leptin5) that increase hunger and appetite. Besides feeling unpleasant, this leads many dieters to eat more than they realize, undermining fat loss. Multiple studies also suggest that low leptin levels increase reward-seeking behavior. Basically, food becomes more appealing and harder to resist.
Low leptin is also related to depression6, anxiety, and perceived stress, all of which can make it harder to stick to your diet goals.
For all these reasons, periodically boosting your leptin via carb refeeds should make dieting feel less challenging. Beyond that, there’s also the psychological factor of knowing that you don’t have to strictly adhere to a diet indefinitely. Although it might seem counterintuitive, research confirms 78that giving yourself planned breaks can help relive the doldrums of dieting and actually increase your adherence in the long term.
Who Should and Should Not Consider Incorporating Carb Refeeds
There’s no evidence that carb refeeds are necessary or optimal if weight loss is your goal. Like so many things, this is going to be an n=1 situation. They might help, hurt, or be neutral depending on the individual.
First and foremost, if it ain’t broke, don’t fix it. If your current diet is working just fine, you feel great, and you’re losing weight, you don’t need carb refeeds. (By the way, if you’re impatient because you’re losing slowly, I haven’t seen any evidence that they will speed up weight loss.)
Likewise, they generally aren’t recommended for people who still carry a significant amount of body fat. There’s no real guidance as to what constitutes “significant amount,” unfortunately. As a rule, though, leaner individuals are more likely to benefit from the hit of leptin because they have less adipose tissue to produce it on a day-to-day basis.
DO: Reasons to experiment with carb refeeds include:
You’re experiencing a weight loss plateau. This means several weeks of no change in weight or body measurements despite nothing else changing. This isn’t a guaranteed strategy, of course. There are lots of reasons weight loss can stall, not all of them related to leptin or diet adherence. It’s certainly worth a try, though.
You’ve been low-carb and/or calorie restricted for a while, and you’re experiencing other signs of hormone dysregulation. These include menstrual irregularity and sleep9 disruptions, among others. Depending on how severe your symptoms, you might need more than the occasional carb refeed. For mild symptoms, an occasional refeed might help.
You’re sick of dieting. Mixing it up with carb refeeds (which are not the same as “cheat days”) can relieve the dieting fatigue.
DON’T: Other instances when carb refeeds are not advised are:
For people who are using low-carb or keto therapeutically, such as for epilepsy or Parkinson’s, unless advised by their health care practitioners.
For people who are extremely insulin resistant.
How to Implement Carb Refeeds
No matter what strategy you use, you want to refeed with nutrient-dense, Primal-aligned foods. We’re talking sweet potatoes, potatoes, beets, baked goods made with almond or coconut flour if you want, in-season fruit, quinoa, maybe legumes if they work for you. If you want to eat some rice (sushi!), no judgement here.
Primal carb refeeds aren’t just an excuse to “cheat” (a term that I hate). You’ll see carb cycling protocols that allow, even advocate, eating copious amounts of junk food (another term I don’t love) on refeed days. Since our goal here is metabolic health and hormone balance, stick to the same Primal foods that support those goals, just with more carbs.
How Many Carbs Should I Add?
If you look at the literature on carb cycling, you’ll find various opinions. Depending on who you ask, it can be upwards of 300+ grams per day. Again, though, these come mostly from protocols aimed at physique and other athletes, and these high carb recommendations are for men who are already quite lean. It’s not clear how they apply to the average woman looking to kickstart their weight loss.
As usual, it’s also hard to find research on people who follow a low-carb Primal or paleo approach. In this oft-cited study,10 for example, the control diet was a mainly liquid diet supplemented with orange juice, yogurt, and cream that came in at an average of 224 grams of carbs per day. In the carb overfeeding condition, which was shown to boost leptin, the average daily carb intake was 394 grams—way more than the average Primal eater probably consumes.
In the absence of solid research-based recommendations, you’ll have to experiment. A good place to start is bumping up to twice your normal daily intake by adding nutrient-dense carbs to one or two of your meals, and increasing as necessary. If you want to be scientific about it, log your food and also keep track of metrics like weight, sleep, and energy. Play around with the frequency of carb-ups, as well as the amount of carb you add, and see what works best.
Should You Increase Carbs, Calories, or Both?
Technically, carb refeeds don’t have to involve more calories. Some protocols state that you should reduce fat on carb-up days so that your total caloric intake stays the same. Others specifically recommend adding carbs and increasing calories by a fixed amount.
Unfortunately, we don’t have enough studies to break down the separate effects of carbs and calories here. In theory, both should signal to the body that energy is available, but carb intake uniquely boosts leptin. Once again, experiment to see what works for you. To start, I’d recommend allowing your calories to increase on refeed days. You might dial back your fat a little, but I wouldn’t overthink it, especially if you’re already low-carb or keto. Adding 50 or 75 grams of carbs is 200 to 300 calories. That might be less than your typical caloric deficit. Even if you add more, it’s unlikely to negatively effect weight loss if we’re talking occasional refeeds.
I know that many dieters are afraid to increase their calories for fear of “undoing” their progress. That fear seems to be unfounded. Multiple studies confirm that intermittent dieting—mixing periods of caloric restriction with eating around your maintenance calories—is no worse11 for losing weight than continuous calorie restriction. It may even be advantageous12 for weight loss, and fat loss specifically.
How Often Should I Refeed?
In terms of how often to refeed, you have some options:
Add in carbs whenever you plateau
Carb cycling on a schedule
Carb cycling around your menstrual cycle
Eating carbs intuitively
Add in Carbs Whenever You Plateau
If you’re actively trying to lose weight, one option is to wait until you hit a plateau—at least a couple weeks when the scale stops moving—then add a day or two of higher-carb Primal meals to see if that moves the needle.
Carb Cycling on a Schedule
As I said up top, some carb cycling strategies involve fixed periods of lower- and higher-carb eating. Often this looks like eating low-carb during the week and then doing one or two higher-carb days on the weekend. This is more convenience than science though. There’s no reason you can’t do 9/1 or 12/2 or any other pattern that works for you. You don’t even need to take a whole day. Some people just do one high-carb meal per week and feel great.
Obviously this strategy is more of a lifestyle than an acute tool for breaking through a weight-loss plateau. This is for people who don’t do well with continuous dieting or who find it easier to stick to their goals when they have planned deviations. It is akin to the idea of a cyclical ketogenic diet, although you don’t have to be keto to use carb cycling.
Carb Cycling Around Your Menstrual Cycle
Another carb cycling strategy is timing carbs strategically around your menstrual cycle.
This strategy isn’t specifically geared at weight loss but rather supporting the whole hormonal system, but it potentially allows you to kill two birds with one stone. There are different approaches here, but a common one is increasing carbs 4 to 5 days post-ovulation (around days 19 and 20 of your cycle) and on the first couple days of your period. These are times when your leptin levels naturally dip, so you could possibly benefit from the boost. Some women prefer instead to add carbs around ovulation, days 13 to 15. Again, see what works be for you.
Eating Carbs Intuitively
Finally, you can wait until your body starts calling out for carbs and respond appropriately. In my opinion, intuitive eating is one of the goals of a Primal diet and lifestyle. When we improve hormone balance and tap into how good it feels to nourish ourselves with nutrient-dense foods, we should be able to trust when our inner voice says, “Hey, I could use some starchy vegetables here!”
Eating carbs intuitively isn’t the same responding to sugar cravings or eating something off plan just because it “sounds good.” I think we can all recognize the difference between listening to our bodies and eating purely for pleasure. (You’re more than welcome to do that too, but it’s not what we’re talking about here.)
Intuitive carb refeeds are probably going to work best for people who have been on the Primal train for a while and who generally feel pretty in tune with their bodies. Women who are dealing with chronic health issues or hormone imbalances might need something more structured.
Note that this is a different question than carb timing, which Mark covered recently. Carb timing is about when to eat your carbs during the day.
Don’t Be Afraid to Experiment
I’m a big fan of experimenting with your diet. There is so much bioindividuality, it’s impossible to find a one-size-fits-all approach. The best strategy for you is the one that hits that sweet spot where you to feel your best and also enjoy how you eat.
Moreover, I’m going to go out on a limb and say if you’ve been low-carb for so long that you’re afraid to consider eating even nutrient-dense, Primal-aligned carb-y foods like sweet potatoes, you should challenge yourself to try a carb refeed and see what happens. I’m not talking about people who know they feel better eating very-low-carb and simply don’t have the desire to switch it up. I’m talking about people who have a mental block around the very idea of carbs. We don’t want people to get “stuck” in a low-carb paradigm to the point where they feel unable to enjoy otherwise nutritious foods just because they have more carbs than, say, broccoli.
Finally, although their are good reasons to try carb refeeds if your current low-carb diet isn’t working the way you want, it’s only one of many things you might try. In particular, if you haven’t also gotten your sleep and stress in order, make those priorities as well. Carb refeeds can only do so much if you don’t have a solid foundation of healthy habits in place.
Tell us: Have you had success implementing a carb cycling approach? What works for you? What are your favorite foods to use to increase carb intake?
Lindsay Taylor, Ph.D., is a senior writer and community manager for Primal Nutrition, a certified Primal Health Coach, and the co-author of three keto cookbooks.
As a writer for Mark’s Daily Apple and the leader of the thriving Keto Reset and Primal Endurance communities, Lindsay’s job is to help people learn the whats, whys, and hows of leading a health-focused life. Before joining the Primal team, she earned her master’s and Ph.D. in Social and Personality Psychology from the University of California, Berkeley, where she also worked as a researcher and instructor.
Lindsay lives in Northern California with her husband and two sports-obsessed sons. In her free time, she enjoys ultra running, triathlon, camping, and game nights. Follow along on Instagram @theusefuldish as Lindsay attempts to juggle work, family, and endurance training, all while maintaining a healthy balance and, most of all, having fun in life. For more info, visit lindsaytaylor.co.