Low-carb diets have been popular recently, partially due to the perception that they help with weight loss. One way they could conceivably do this is by boosting resting metabolic rate. Your body has a baseline metabolic rate at which it burns energy. This is called resting metabolic rate and it’s a measure of how much energy your body uses when at complete rest. A faster resting metabolic rate gives you an advantage if you’re trying to lose weight. If you have a higher resting metabolism, your body burns through energy stores faster.
Can a certain diet or supplements boost your metabolism? Some weight loss products, the so-called fat burners, promise to elevate your resting metabolism, but most have only a minimal impact. Some contain stimulants that boost metabolic rate short term, but these products also carry risks. So, your thoughts might turn to diet and the macronutrient composition of what you eat as a way to boost your metabolic rate. What does science say about this issue?
Can a Certain Type of Diet Raise Your Metabolic Rate?
Is eating low carb a metabolism booster? A recent study published in the British Medical Journal reveals that cutting carbohydrates and consuming more fat may modestly boost resting metabolic rate. In the study participants who followed a low-carb diet for 6 months boosted their resting metabolic rate by 250 calories per day. In other words, they burned an additional 250 calories just by changing their diet. One problem with losing weight is that weight loss and calorie restriction can slow resting metabolism and make it harder to maintain any weight that was lost. Over 80% of people who lose a significant amount of weight gain it all back. Maintaining the weight, once lost, can be a challenge! So, anything that helps to elevate or prevent a diet-induced reduction in resting metabolic rate is beneficial.
This isn’t the first study to show that reducing carbs helps with weight loss. A meta-analysis of 23 studies that compared low-carb and low-fat diets found that low-carb diets offer an edge, at least short term. But, longer term, studies also show that weight loss is similar with a low-fat and a low-carb diet. It’s possible that low-carb diets offer a weight loss advantage early on, but either low carb or low fat is equally effective long term. Low-carb diets may also improve lipids by lowering triglycerides and increasing HDL-cholesterol.
How might low-carb diets help with weight loss? Low-carb diets lower the insulin response to a meal and may increase insulin sensitivity. However, there could be a floor below which you can’t go if you want to maximize insulin sensitivity. Some research suggests that when you drop below 10% carbs, insulin sensitivity falls.
Now, the Potential Downsides
While a low-carb diet may help with weight control short-term, there are some downsides. A recent study followed nearly 25,000 people over time to see how they fared on a low-carb diet. In fact, those who ate low-carb had a 32% higher death rate. Although a low-carb diet may boost your metabolism, it’s not clear whether it’s safe to follow this extreme approach to dieting long term.
A low-carb diet may have other unfavorable effects on the body. For example, low-carb fare is usually low in fiber. Fiber-rich foods, like fruits and vegetables, help to foster a healthy gut microbiome. In one study, scientists used a human gut simulator to look at the impact a low-carb diet could have on the gut microbiome. They found that when people drastically cut carbs, it led to a reduction in short-chain fatty acids and antioxidants in the colon. Scientists believe these short-chain fats have a favorable impact on the lining of the large intestines and may help protect against colon cancer. So, eliminating one macronutrient from the diet can have an unforeseen impact on other systems.
Don’t Eliminate the Good Stuff!
Let’s face it, many of the most nutrient-dense foods are fruits and vegetables. When you follow a low-carb diet, you can eat some non-starchy vegetables, but most fruits, with the exception of berries, are off the menu. It’s an extreme approach and one that’s difficult to sustain long-term. Some people experience short-term fatigue and flu-like symptoms when they first start a low-carb diet. Is there a middle ground where you can enjoy the metabolic boost of a low-carb diet and still get the health benefits of fruits and vegetables?
Some individuals who want the best of both worlds have taken up carb cycling. They have days where they eat a low-carb diet and days where they boost their carb intake and enjoy more veggies and fruit on others. For example, they select 3 days during the week to cut carbs and 4 days to eat a higher carb diet of unprocessed, whole food carb sources. Some athletes schedule higher carb days for workout days when they need the extra carbs to fuel high-intensity exercise. On low-carb days, they stick to a diet that’s higher in protein and fat but low in carbs.
There may be additional benefits to using this approach. Too often, people who are trying to lose weight reach a plateau where the weight loss stops. Cycling carbs may help to prevent frustrating weight loss plateaus, although more research is needed.
The other option is to be more selective about your carbs. Don’t go the low-carb route, but make sure the carbs you’re eating are unrefined and remove all sugar from your diet. Doing these things alone can improve your metabolic health and help with weight loss, as your insulin level will drop. This is a more sustainable approach for most people than going on a low-carb diet. The most important thing is to choose a diet you can stick with long term. It has to be sustainable!
The Bottom Line
There is some evidence that a low-carb diet boosts resting metabolism short-term, but the long-term impact of drastically reducing carbs isn’t clear. The best option might be to be more selective about your carbs rather than eliminating them entirely, especially when it comes to fruits and vegetables.
New York Times. “How a Low-Carb Diet Might Help You Maintain a Healthy Weight”
BMJ. 2018: 363:k4583.
HealthLine.com. “23 Studies on Low-Carb and Low-Fat Diets — Time to Retire The Fad”
Medical News Today. “How a low-carb diet might impact gut health”
J Am Coll Nutr. 2004 Apr;23(2):177-84.
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