There is a lot of contradictory advice when it comes to how many carbohydrates you should eat to lose weight. Many health and fitness authorities contend that low carbohydrate (low carb) dieting is the way to go. Others argue against it as being unsustainable and just a fad. Many still maintain that “it depends”. So how can you tell if you’re the type of person who should be eating a low carb diet? And how do you determine how many carbs should you eat to lose weight? I’ll attempt to answer both of these questions in this article.
If you're only interested in the actual numbers, skip to the "How Many Carbs Should You Eat" section.
The Draw of Low-Carb Diets
Weight loss is often thought of as a question of calories. Eat less, burn more, and you'll lose weight. This is very true in theory, but not very useful in practice. The problem with focusing on calories is that it ignores hormonal biofeedbacks. It ignores the fact that we don’t eat calories, we eat food. And food is so much more than just calories.
One of the main draws of low-carb diets is that they positively impact hormonal balance. Hormones are the key messengers that tell your body to burn or store fat, remain full or feel hungry, crave some foods but not others, feel motivated to exercise or drag your workouts, feel energized or fatigued, and much more. Hormones even impact your mood.
Countless studies have shown that when people reduce their carbohydrate intake, they also spontaneously reduce their caloric intake. (1) A lot of foods available on low-carbohydrate diets come from protein, which has been shown to be more satiating than either carbohydrate or fat. (2, 3) There is also plenty of evidence that protein reduces hunger and cravings (4, 5), requires more calories to digest than carbohydrates or fat (6), and can even help with gaining muscle mass (7).
Carbohydrates and Hormones
The primary hormone that regulates your appetite and food intake is called leptin. Leptin communicates with your brain about how much fat you have stored and when you should stop eating. (8) When your fat stores are full, leptin shuts off your hunger switch and tells your brain to start burning the stored fat instead. As your fat stores decrease, leptin sends a signal that it’s time to eat again. You eat, replenish the fat mass, and leptin goes up again.
This seemingly effective physiological system can be easily disrupted if leptin can't communicate with the brain properly. If leptin can't get to the brain, it doesn’t shut off the hunger response irrespective of how much fat is circulating in the blood. (9) Many overweight people find themselves in this very situation: high levels of leptin (and circulating fat) but still feeling hungry.
Where does the low-carb diet fit in? Well, studies have shown that the primary culprit behind the disrupted leptin-brain communication pathway are triglycerides (fat circulating in the blood). (10) Can you guess what the main driver of elevated triglyceride levels is? Carbohydrates, that's right. Especially the quick-digesting (high in glycemic load) carbohydrates. (11, 12, 13). Low-carb diet, on the other hand, drives triglyceride levels down. (14)
Insulin is another important hormone involved in weight management. It has many functions throughout the body, but its main function is to control blood sugar levels after a meal. Insulin rises any time you eat. However, the more refined and processed the carbohydrate, the faster and in higher amounts insulin rises. Another thing insulin does is, it tells your body to stop breaking down stored fat for energy and start using the energy from the food you just ate. (15) Insulin also tells your fat cells to store some of the energy from food for later. (16)
The idea behind the low-carb diet is that decreasing carbs lowers insulin levels, which causes the body to burn stored fat for energy and ultimately leads to weight loss.
That being said, some scientist don't believe this to be true. As an obesity researcher Stephan Guyenet states,
“If you eat a meal of 500 calories of carbohydrate, you will burn that carbohydrate under the direction of insulin, which will also make sure body fat mostly stays inside your fat cells during the process. If you eat a meal of 500 calories of fat, you will burn fat instead of carbohydrate, but since you just ate fat, you aren't dipping into your body fat stores any more than you were when you ate carbohydrate. So even though insulin temporarily suppresses fat burning and the release of fat from fat cells when you eat carbohydrate, at the end of the day if you ate the same number of calories you end up with the same amount of fat in your fat cells either way.” (17)
The mechanism of greater weight loss on a low-carb compared to a low-fat/high-carb diet is unknown. (18, 19)
How Many Carbohydrates Do You NEED?
Technically speaking, none. (20) Your body can produce glucose (sugar) from other energy sources like fat and protein. You might have heard that the minimum of carbohydrate requirement for your brain to function properly is 130 grams per day. Well, that’s a myth. According to the US Institute of Medicine’s Food and Nutrition Board,
“the lower limit of dietary carbohydrates compatible with life apparently is zero, provided that adequate amounts of protein and fat are consumed”. (21)
However, from a practical point of view, your body does prefer carbohydrates for energy. Another reason why zero-carb diet isn’t a good idea is nutrition. Completely avoiding carbohydrates eliminates many healthy foods, such as fruits, vegetables.
How Many Carbs Should You Eat To Lose Weight?
The most important thing to remember here is that there’s no one-size-fits-all approach. While some people thrive on low-carb diets, others don’t. There are numerous factors that determine what is optimal for each person. These include variations in gene expression, the microbiome, age, gender, lifestyle, activity level, body type, disease state, health goals, geography (e.g. latitude and climate), and more.
There’s a range of carbohydrate levels and everyone will feel best at a different level. To determine how many carbohydrates you should eat, I’ll walk you through a simple process.
Consider Medical Conditions
The first factor to consider is whether you’re suffering from any medical condition. Those with underlying medical conditions, such as obesity, blood sugar imbalances (diabetes, high blood sugar), neurological disorders (Alzheimer’s, dementia, epilepsy, Parkinson’s, stroke), mood disturbances, polycystic ovarian syndrome, small intestinal bacterial overgrowth, or even some forms of cancer, generally benefit from a very low (<10%) to a low (10 – 15%) carb diet. (22)
On the other hand, those suffering from medical conditions such as adrenal fatigue, gut dysbiosis, hypothyroidism, or those who are physically very active (athletes), pregnant, or breastfeeding, will most likely feel better on a more moderate (15 – 30%) to a high (>30%) carb diet. (23)
Find Your Carbohydrate Tipping Point
The second step in determining how many carbs you should be eating is to find your carbohydrate tipping point. The carbohydrate tipping point, as the Metabolic Effect calls it, is an individual measure of starch/sugar you can eat to supply energy for your daily activities, but not over produce insulin to engage fat burning. (24) For fat loss, begin with a low to moderate carb diet (around 15% of carbs per day) and adjust from there.
Observe and Adjust
An easy way to find out if what you’re doing is working is to check your body’s hormonal biofeedback sensations, such as hunger, cravings, energy levels, mood, sleep, and digestion. Track your meals and take notes about how you’re feeling. You shouldn’t be hungry, experience cravings, lack energy, feel anxious or irritable, have problems falling and staying asleep, or experience gas and bloating.
Keep tweaking until you find your carbohydrate tipping point. That is, you’re losing fat and all your biofeedback sensations are in balance. Once you find it, you want to stay there.
If your biofeedback sensations are balanced, but you aren’t losing fat, you might want to bring your carb intake (especially starch and sugar) down. If you are losing weight, but your hormones are imbalanced, you might want to bring your carb intake (especially fiber) up. Keep experimenting until you find what works for you.
Why Eliminating Carbs Doesn’t Always Lead to Weight Loss
When you severely restrict or eliminate carbohydrates from your diet, your body has to convert fat and protein to glucose via a process known as glucogenesis. (25) The signal to do this comes from low insulin and high glucagon levels. Low insulin and elevated glucagon signal to the fat cells to release their fat for energy.
However, this process hinges upon one condition – your body’s energy needs. While it’s true that low insulin and elevated glucagon levels allow fat to come out of the fat cells, the fat comes out only if it’s needed. If you’re meeting all your body’s energy requirements with the food you’re eating, your body doesn’t need to tap into its energy stores no matter how severely you restrict your carbohydrate intake.
I’m not advocating for the traditional “calories-in-calories out” model here. The human body is a complex system and much more needs to be considered when it comes to weight loss. However, if you regularly feed your body more energy than it burns (creating a calorie surplus), you will gain weight. On the other hand, if you regularly feed your body less energy than it burns (creating a calorie deficit), you will lose weight. There’s no way around it.
As with any dietary approach, low-carb diets don’t work for everyone. It's important to do some experimenting to determine what works for you. As a rule of thumb, if you're sedentary and/or overweight, you're most likely going to do better on a low-carb diet because your body doesn't need all the energy carbohydrates provide. On the other hand, if you're physically active or pregnant/breastfeeding, a higher-carb diet will be a better choice for you.
What's important to keep in mind is that a low-carb diet isn’t just about weight loss. It's also supposed to improve your health. Pay attention not only to how many but also the type of carbohydrates you're eating. Carbohydrates like fruits, vegetables, some grains, and legumes are full of fiber, vitamins, minerals, and phytochemicals that are beneficial for your health. Others, like baked goods, candy, or sweetened beverages, do not offer much nutritional benefit at all. Whenever you have the chance, choose carbohydrate sources that come from whole foods and include the highest fiber to sugar/starch ratio.
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