Whether lowering your intake of one nutrient or increasing your intake of another nutrient leads to weight loss isn't clear. However, lowering your intake of certain carbs is a step in the right direction. Ultimately, weight loss depends on your overall calorie intake and the quality of your diet as a whole.
The number of grams of carbs you eat per day doesn't determine weight loss. Your calorie intake and all the foods you eat make the biggest difference.
Weight Loss Explained
There are a lot of misconceptions about how weight loss occurs. First of all, "weight loss" is a misnomer; most people don't want to lose weight (the number on the scale), they want to lose fat. Those are totally different concepts. Your body weight is the combined weight of fat mass, lean muscle mass, bones and other tissues and fluids. If the number on the scale is going down, you're not necessarily losing fat.
So, how do you lose fat, specifically? There are many different theories on the best way to burn fat, but most aren't scientifically proven. What is widely considered the primary path to fat loss is lowering calorie intake below calorie expenditure. This creates a calorie deficit that causes the body to cease fat storage; eventually, it will need to tap into stored fat, which it will burn for energy.
Now, this is a very basic explanation of fat loss. In truth, it involves myriad of other factors that affect how easy or hard it is for you to lose fat, how quickly you can lose fat, where you lose fat from, etc. Your genetics play a major role, as does your age and sex. If you have certain medical conditions, such as thyroid disease, or you take certain medications, fat loss can be stubborn, if not seemingly impossible.
The Role of Carbs
Carbs are one of the three macronutrients, in addition to protein and fat. These are called "macro" nutrients because you need them in larger amounts than vitamins and minerals, which are "micro" nutrients.
Carbs are the body's main source of energy. When you eat carbs, they are broken down into glucose, which is absorbed into the bloodstream and delivered throughout the body where it is needed. Carbs power your daily activities and physical exercise, and your brain uses about 20 percent of the energy from carbs, according to an article in Trends in Neurosciences in October 2013.
Carbohydrates also play other roles. A type of carbohydrate called dietary fiber is critical for healthy digestion, regular bowel movements and the prevention of colon cancer. Fiber also helps control cholesterol and blood sugar levels and aids weight management, according to the Mayo Clinic.
The Carbohydrate Conundrum
If carbs do all those good things, then why the low-carb craze? There are reasonable explanations for why people malign carbs and some other less reasonable explanations that science has not yet confirmed. The soundest explanation is that not all carbs are created equal. There are "good" carbs and "bad" carbs.
Good carbs are those found in nutrient-rich foods such as fruits, vegetables, whole grains, beans, nuts and seeds. These foods are fiber-packed and loaded with other valuable nutrients that give you energy and fight disease. Due to their complex chemical structure, they take your body longer to digest, which slows the release of glucose into the bloodstream and provides a sustained, steady supply of energy.
Bad carbs are found in sugary, refined, processed junk foods, fast foods and sweetened drinks. These carbs offer little nutrition and a lot of calories. Think cupcakes, candy or potato chips.
Your body metabolizes these carbs into glucose very quickly. The sugars flood your bloodstream, creating precipitous blood sugar levels that your cells, with the help of the hormone insulin, must struggle to control. This rush of sugar provides a quick burst of energy, but it dissipates quickly. Eating a lot of these simple carbs can lead to unstable energy levels as well as hunger soon after eating, which can make it hard to control your calorie intake and lose fat.
Carbs and Fat Loss
Whether or not you want to lose weight, it's crucial to limit your intake of simple carbs. A healthy diet includes lots of fresh fruits and vegetables and moderate amounts of whole grains, beans, nuts and seeds. The majority of carbohydrates should come from whole, unprocessed foods as close to their natural state as possible.
A healthy diet should not include the "bad" carbs, except for the occasional treat. These bad carbs include foods such as:
- Refined grains, such as white rice
- White flour
- Pastries, cookies, cakes or candy
- Soda and sweetened beverages
- French fries, potato chips and other snack foods
- Sugary cereals and flavored yogurt
- Fruit juice (a concentrated source of sugars)
- Many salad dressings, sauces and condiments containing sugar
- Table sugar, and all the varieties of sugars that may appear on ingredients labels, such as high-fructose corn syrup, maltose, dextrose and brown rice syrup
Often, if you cut out these foods, you don't need to count calories or carbs. Especially if you have been eating a lot of these foods, replacing them with healthy carbs may significantly decrease your calorie intake and help you lose fat. However, some people choose to take carb-cutting to another level.
For example, many people shun grains, even whole grains, because they are high in carbs. There's no evidence that eating grains in appropriate portions stalls fat loss. Eating too much pasta, rice and bread, even if it's whole grain, can inhibit fat loss. But so can eating too much of anything.
How Much Do You Need?
According to the National Academy of Medicine, adults should consume a minimum of 130 grams of carbs a day. Ideally, you should get 45 to 65 percent of your daily calories from carbs. How many carbs you need is an individual matter based on your calorie intake, activity level and health status. Your doctor or a nutritionist can help you find a number that works for you.
More importantly, how many calories do you need for weight loss? That's also highly individual and based on the same factors that determine your carb intake. As a general rule, creating a calorie deficit of about 500 to 1,000 calories a day can help you lose about 1 to 2 pounds per week, according to the National Institutes of Health. This deficit can include calories cut from your diet and calories burned with exercise.
If you want to lower your carb intake, try starting with a daily goal of 45 percent of your weight loss calorie needs from carbs. See how that makes you feel and whether it helps you shed fat, and then make adjustments from there. In the end, you may find that you have more weight loss success just by making healthy food choices, eating proper serving sizes, getting plenty of exercise and keeping your daily calories in check.
- CDC: "Finding a Balance"
- NIH: "Factors Affecting Weight & Health"
- Washington State University: "Nutrition Basics"
- Trends in Neurosciences: "Sugar for the Brain: The Role of Glucose in Physiological and Pathological Brain Function"
- Mayo Clinic: "Dietary Fiber: Essential for a Healthy Diet"
- StatPearls: "Physiology, Carbohydrates"
- American Diabetes Association" "How Your Body Uses Glucose and Insulin"
- American Heart Association: "Carbohydrates"
- UCSF: "Hidden in Plain Sight"
- National Academy of Medicine: "Dietary Reference Intakes: Macronutrients"
- NIH: "Key Recommendations"