The fitness industry is filled with conflicting information, particularly in application to nutrition. Professional athletes, popular celebrities, and average Joe’s alike have been seeking the optimal nutrition approach to support their fitness goals.
For many years, researchers believed that a diet low in dietary fat and high in carbohydrates was superior for both weight loss and overall health. In more recent years, a dramatic increase in the popularity of mainstream low-carbohydrate diets (i.e. Atkins, Paleo, and Keto) has contradicted these earlier beliefs, and now has many fitness enthusiasts scrambling to rid their diets of grains, starches, and highly-palatable sources of carbohydrates.
The question now becomes, is this really the best strategy for weight loss? Fortunately, a tremendous amount of research has been conducted over the last several decades pertaining to this exact topic, and this article sheds a lot more light onto the mechanisms behind the staggering transformations we’ve seen in recent years from individuals adopting a low-carb approach.
History Of Low-Carb Diets
Low-carb diets are not actually such a new concept. In the course of human history, many early civilians adopted diets high in meats, vegetables, fruits, nuts and seeds, which in total generally favor a lower-carb nutritional intake. In mainstream society, low-carb diets became popular as a tool for improved body composition and faster weight loss largely in-part to name-brand diets established in the 19th and 20th centuries.
Back in 1863, a formerly obese English undetaker named William Banting published his own low-carb diet book in support of the positive results he obtained from his nutritional approach . Many years later, Dr. Robert Atkins established the now-infamous Atkins diet, which has served as the first of many name-brand diets that have gathered substantial recognition over the past 40+ years.
Let’s take a look at what the data shows related to the efficacy of five of the most-popular low-carbohydrate diets out there right now: the ketogenic diet, the paleo diet, the atkins diet, the mediterranean diet, and the carnivore diet. I’ll start with a brief overview of each diet, followed by an analysis of their effectiveness and relevant benefits comparison to higher-carbohydrate diets.
Mainstream Name-Brand Low-Carb Diets
The ketogenic diet is a high-fat, moderate-protein, and very-low-carbohydrate diet that has exploded in popularity in recent years. Originally used medically as a nutritional approach to help treat Epilepsy , the diet has gathered a ton of recognition in the fitness industry as a means of inducing weight loss and various other desired health benefits, including improved appetite regulation and insulin sensitivity, as well as a decrease in inflammatory measures. This is not your typical “low-carb” diet approach, with an extremely high percentage of daily calories (close to 75) coming from dietary fat, as opposed to an almost zero-carb approach (<30 grams of net carbs per day). Even most of the other diets covered later in this article allow for substantially greater amounts of carbohydrates in the daily diet. The goal of keto is to shift the body into a state of ketosis, which happens when blood ketones are higher than normal due to dietary changes. We can get into ketosis a few different ways, but the most popular method today comes from the use of the ketogenic diet. With a shift in one’s caloric consumption comes by replacing carbohydrates with mostly dietary fat and a little bit of protein for an extended period of time, blood glucose supplies fall to extremely low levels, and the production of ketone bodies is accomplished through ketogenesis .
Paleo is not inherently a low-carb approach, but due to the nature of the individual food restrictions it places within its criteria, often times individuals’ diets are comprised of a much higher percentage of protein and carbohydrates. The bulk of the diet typically includes meat, vegetables, fruits, nuts, and other foods that were originally consumed by the “modern human”. On top of that, there’s a long of foods that are off-limits: grains, all dairy products, foods containing added sugars and salt, and popular beverages coffee and alcohol.
As I discussed earlier, the Atkins diet was popularized in the 1970’s and gathered additional attention in the early 2000’s, with the goal of using carbohydrate restriction as a means of inducing weight loss. The basic premise of the diet is a dramatic reduction in refined carbohydrates and saturated fat, replacing these foods with unprocessed whole foods. The company today offers several variations and nutritional products associated with their brand, all in-line with adopting a low-carb dietary approach.
The Mediterranean diet tends to be pretty similar to Paleo, although with far-less food restrictions and a greater allowance for the consumption of “processed” foods. Based largely on the eating habits of countries such as Greece, Spain, and Italy, staples of the diet include high consumption of fish, fruits, vegetables, olive oil, dairy and wine. Originally viewed as a healthier alternative to the Western diet, in recent years it’s been associated as a fad diet for weight loss purposes in other parts of the world.
Probably the most-recent mainstream low-carb approach that has gained substantial recognition in the past couple of years is the Carnivore diet. As the name implies, the only foods allowed in this nutritional approach are meat and other selective animal products, resulting in quite literally a zero-carb diet. Similar to Paleo, proponents of the diet believe this method of eating to fall in-line with our “natural” dietary history, making it a much more suitable approach for weight loss and optimal human performance. Now that we have an overview of what each diet entails, we can take a look at how they tend to fair based on the body of nutritional research that has compiled over the years.
How Do They Compare To Regular Diets In Research?
Since this article is specifically comparing various carbohydrate intakes for the sole purpose of fat loss, we’ll keep the research related to just that. There is a good amount of data suggesting benefits of low-carbohydrate diets on other health parameters and performance markers, but it’s not directly relevant to the scope of this discussion.
Research directly on the ketogenic diet for its effects on weight loss is relatively limited. Because the diet has been traditionally used in the medical field, a lot loss emphasis has been placed on its effectiveness as a weight-loss diet in the long-term. Nevertheless, the data that has been gathered is pretty inconclusive on its usefulness.
In a 2013 meta-analysis comparing a ketogenic diet vs. a low-fat diet for long-term weight loss, the authors found that the ketogenic diet provided a greater decrease in bodyweight, overall blood pressure, and triglycerides compared to the low-fat diet . Sounds like an easy answer there, right? Unfortunately, not all of the data gathered was all that beneficial. Along with these findings in the study though were that changes in bodyweight fell to less than two pounds, and that compliance to the ketogenic diet declined over time .
Dietary adherence has consistently shown to be a major predictor of weight loss success in the long-run, regardless of the individual macronutrient composition of the diet . Interestingly though, the ketogenic diet appears to be particularly effective for appetite regulation, even though the exact mechanisms are not exactly known. In a systematic review published in 2015, the authors noted a profound reduction in hunger in the ketogenic group, theorizing mainly due to changes in hunger hormones such as ghrelin and leptin . Similar findings were determined in a 2013 review paper, though the authors noted a dramatic increase in appetite during the two-week period that they came off of the diet .
Overall, it appears that the ketogenic diet has some utility for weight loss, though research is still limited.
Literature on the usefulness of Paleo for weight loss purposes is not well-supported. Multiple short-term studies (less than six months each) suggest its benefits for weight loss and other positive health parameters , although a follow-up study concluded that the weight loss caused by the diet was the result of calorie restriction, rather than any unique properties in the diet itself .
Additionally, along with each of the low-carbohydrate diets that include specific restrictions on individual foods, strictly following the Paleo diet poses the risk of nutrient deficiencies. This diet does not allow for the consumption of grains of any sort, even less-processed whole grains that have commonly been met with positive support in research on overall cardiovascular health and a healthy body weight .
Another nutrient of particular concern is calcium, which is extremely limited on Paleo due to the exclusion of all dairy products in the diet. Not only does a lack of calcium pose the risk for osteoporosis and other diseases , but interestingly dairy products actually perform extremely well in research on measures of appetite regular and overall body composition , bringing additional skepticism of the efficacy of eliminating an individual food group for weight-loss purposes.
Overall, no data currently exists supporting the use of Paleo as a superior method for weight-loss in a calorie controlled-setting, and instead brings into question its usefulness in supporting overall health.
Similar to most commercial weight-loss diet plans, very limited research exists on the efficacy of Atkins as a useful long-term strategy, with very little evidence of substantial body composition changes . Just like Paleo, most data points to the indirect benefits of the Atkins diet promoting weight loss, including highly-satiating food choices and reduced spontaneous food consumption . Nevertheless, the positive changes in body composition through the adoption of this diet are much-more closely related to the accompanying caloric deficit with such a nutritional approach than any individual mechanisms from the diet itself, again bringing into question how well the Company’s claims seem to be supported in the scientific literature. As with other nutritional and dietary supplement brands, it’s important to be wary of the potential biases and lack of evidence from the claims made about individual products.
Interestingly, the Meditteranean diet tends to fair incredibly well compared to the other well-recognized diets in this article in the literature analyzing the nutritional approach. Multiple studies have reported its association with a decreased risk of cardiovascular diseases and diabetes . Additionally, as mentioned earlier, the Meditteranean diet tends to be far-less restrictive compared to other low-carb dietary approaches, bringing along a reduced risk in the development of substantial nutrient deficiencies.
While this all sounds good, it’s important to understand that the mechanisms by which the diet brings along various health benefits are much-more related to the individual food choices that make up the bulk of the diet. A higher consumption of fruits and vegetables (vitamins and minerals), olive oils (monounsaturated fats), dairy and fish (dietary protein) has been extremely well-received in the literature for promoting healthy metabolic health and supporting a reduced risk of various diseases . These food groups also tend to be much-more satiating, leading to a reduced caloric consumption throughout the day , and thereby net fat loss.
Therefore, regardless of the dietary approach one elects to adopt, various aspects of the Meditteranean diet should be incorporated into one’s diet to promote optimal health.
Because the Carnivore has only recently become popularized as a mainstream low-carb approach, there is little-to-no direct research on its efficacy for weight loss proponents. However, since the food choices on this approach are essentially a combination of what you’ll find on the menu for both the Ketogenic and Paleo diets, we can draw many of the same conclusions in relation to how a zero-carb approach works for the sole purpose of fat loss. There are plenty of other benefits to the Carnivore diet argued by its proponents for overall health and its applicability to how we have evolved as humans over the course of time, however almost all of these are unrelated to weight loss purposes.
Instead, the same general conclusions about meat-based, high-protein diets can be attributed to the previously-mentioned literature on the role of similar diets on both appetite suppression and the prevention of food cravings. However, it’s worth noting again that protein intake alone is not the main-determinant for appetite regulation. The combined effects of dietary fiber, total energy density, food palatability, and other psychological factors can all overshadow the additional satiating effect of protein. So while a meat-based diet may provide temporary benefits for controlling hunger levels, it’s also worth considering the long-term implications on diet adherence for maximal longevity of a nutritional approach.
So Why Do They Really Work?
You may still be skeptical of the information presented, despite all of the existing data out there surrounding this subject, particularly due to the thousands of individuals out there who have over the course of their lives seen superior results on their body composition adopting a low-carb approach. However, what’s important to understand here is that correlation does not always equal causation. Meaning that while it is undoubtedly apparent that plenty of people have achieved incredible success on a diet containing very few carbohydrates, it’s not necessarily the carbs themselves that have led to such outstanding results. Here are a few common examples of why a low-carb approach works wonders for so many people.
“Tricking” Yourself into a Calorie Deficit Via Appetite Suppression
This is probably the most common reason why so many low-carbohydrate advocates have developed over time, identifying a lack of hunger as the most profound benefit of their dietary choices. And indeed, when you look at the data on many foods that are staples on low-carb diets, it begins to make sense why such a phenomenon exists. For example, there’s a good amount of research supporting that high-protein diets promote superior satiety and help reduce total energy consumption throughout the course of the day . Being that meat, seafood, and other protein sources are highly-consumed in most low-carb diets, this is a plausible mechanism where such a sensation originates. Additionally, most low-carb approaches limit the consumption of processed and/or simple carbohydrates, and alternatively emphasize the consumption of fruits, vegetables, and selective whole grains.
Due to the fact that both fiber and highly-voluminous foods offer benefits for satiety , this further emphasizes the idea that the cumulative dietary choices available in a low-carb approach assist in regulating hunger levels throughout the day. Since total energy balance is by-far the driving factor for predicting body weight , and the improved appetite regulation benefits from a low-carb approach assist in sustaining that over time, we can see a pretty-evident causation between weight loss and any of the aforementioned low-carb diets.
Dropping Initial Pounds due to a Loss in Water-Weight
Almost everyone will lose weight initially on a low-carb diet when placed in an appropriate calorie deficit, but this does not mean that it is actual fat mass lost during this period of time. This is because the body stores carbohydrates in the form of glycogen within your muscles and liver. When you reduce or even completely eliminate carbohydrates from the diet, glycogen stores go down and you lose a significant amount of water weight. However, once carbohydrates are reintroduced into the diet, you can rapidly gain the weight back . This is a common reason why you see so many individuals “yo-yo” diet throughout the year. Cutting back initially on carbohydrates for a brief period of time, especially in processed and refined variations that are easy to over-consume  almost inherently place an individual in an appropriate calorie deficit. As adherence declines over the course of time, and similar food choices are reintroduced into the diet, weight gain is nearly unavoidable.
Role of the Thermic Effect of Food (TEF)
A final, albeit minor benefit that a low-carbohydrate diet may offer for weight-loss purposes are related to the concept of the Thermic Effect of Food (TEF), also known as diet-induced thermogenesis. This refers to the calories in the food you eat that is used to digest and absorb the rest of the food, while the rest will be burned-off as heat. Your daily energy expenditure consists of three basic components: basal metabolic rate (BMR- the amount of energy your body expends at rest), TEF, and your actual physical activity throughout the day. Current research indicates that the TEF makes up roughly 10% of your daily energy expenditure, depending on the individual .
What’s important to note within the scope of this article is that the energy required to digest each macronutrient varies, with protein ranking the highest at roughly 20-30%, which is substantially higher compared to carbohydrates with a TEF close to 5-10% . As a result, it’s been hypothesized that a high-protein, low-carb approach would work substantially better for weight-loss purposes by increasing one’s metabolic rate compared to other macronutrient combinations. However, it is vital not to lose site of the fact that the TEF makes up such a small portion of your body’s metabolism. Instead, BMR, physical activity, and non-exercise activity thermogenesis (NEAT) are all greater contributors to energy expenditure throughout the day. So while the consumption of the majority of one’s calories in the form of carbohydrates may burn less energy throughout the digestion and absorption process, so long as energy balance is equated throughout the day, there will be negligible differences in body composition results.
What About High-Carb Diets?
We have so much information about both the benefits and potential drawbacks of a low-carb approach, but how exactly do they fare compared to a high-carb approach for weight loss purposes? And perhaps more importantly, where does this idea come from that carbohydrates are inherently a bad choice? Let’s take a look at this from a couple different perspectives.
Low-Carb vs. Low-Fat
In an effort to settle the ongoing debate on the efficacy of low-carbohydrate diets, researchers have conducted a plethora of studies over recent years comparing individuals on such a dietary approach towards a second group adopting a higher-carb, lower-fat approach. A recent meta-analysis from 2018 compared the effects of dieting from both groups. They analyzed 32 different studies where calories were equated, and concluded that both diets resulted in similar metabolic rates and similar rates of fat loss over the course of the weight-loss period .
Another 2018 study on this same subject was led by researchers from Stanford University in conjunction with the US National Institutes of Health (NIH), the Nutrition Science Initiative (NuSI), and a team of nutrition experts . They conducted a year-long study involving over 600 participants, carefully monitoring their adherence with the assigned dietary protocol, and showed no significant weight-loss differences between the two groups. This is such a significant study in the body of literature on this subject matter largely due to the incredibly high sample size and data accuracy that was maintained throughout the study. As it can be seen in the presented studies (and hopefully throughout this entire article as well), is that there truly is no “best diet” when it comes to weight loss. Time and time again, it appears that dietary adherence and a calorie deficit are the two primary factors for sustainable fat loss, and that individual macronutrient combinations are simply used to “fine-tune” the objective of the diet.
So Where Does The “Carbs Are Bad” Phenomenon Come From?
There are a couple different rationales for the supposed dangers associated with a high-carb approach if an individual’s goal is weight loss. The major one being that when we consume carbohydrates, the hormone insulin is secreted throughout the body, and as a result stores the carbohydrates we consume as body fat as opposed to lean tissue. While indeed insulin is an anabolic hormone that regulates blood sugar in the body, high levels of insulin secretion are only seen directly following a meal in healthy individuals. What this means is that over the course of a 24-hour period, it will all balance and net fat loss will remain the same in a calorie-controlled setting. What’s important to note too is that your body can synthesize and store fat even when insulin levels are low , so even people who adopt a low-carb approach are not inherently immune to the potential for additional fat storage.
A pretty obvious rationale behind the potential drawbacks to a high-carb approach too is the seemingly-easy potential for overconsumption of highly-palatable foods, thereby placing an individual in an undesired calorie surplus. Foods like cookies, ice cream, and starchy grains such as rice and pasta are not inherently bad foods for weight loss; however, they tend to be incredibly energy dense for the portion sizes that they provide. The problem with refined carbohydrates is not the insulin spike (since dietary protein also causes an insulin spike), but rather the lack of satiety and a feeling of fullness for the amount of calories taken in for each serving size. As mentioned earlier in the article, this is the reason why fruits, vegetables, and whole grains are “better” options for someone on a weight-loss diet. They are significantly more filling, provide a ton of vitamins and minerals, and much-more difficult to overconsume.
Why High-Carb May Actually Benefit Your Dieting Period
Nevertheless, there may be some practical benefits to keep your carbohydrate intake as high as possible anyway during a dieting period, mainly due to the advantages provided towards training performance and maintaining glycogen stores. In a 1999 paper analyzing strength athletes and the impact of carbohydrate intake on training performance, researchers found that an inadequate carbohydrate intake can impair strength training . Even though the exact low-end of carbohydrate was not defined by the researchers, a paper published in 2011 providing nutritional guidelines for strength sports recommends an intake between 4-7g/kg (roughly 2-4g/lb) of bodyweight for an individual athlete . Importantly though, the individual carbohydrate necessary is highly dependent on the individual’s training modality and dietary preferences, so these numbers should not be copied verbatim.
There’s also good research on varying macronutrient combinations and their effects of the preservation of lean body mass during a dietary restriction period. In a study by Mettler et al. from 2010, they found that a calorie reduction from dietary fat and maintaining carbohydrate and protein intake helped maintain training performance and almost completely eliminate lean body mass losses in trained individuals . Therefore, if the goal of the weight loss period is to maximize fat loss while maintaining exercise performance and muscle mass as much as possible, it may be most-advisable to set protein intake between 1.6 and 1.8kg/b (0.8-0.9g/lb) of body weight, keep dietary fat between 15-30% of total daily calories , and fill-in the remainder of the diet with carbohydrates.
Hopefully it is apparent throughout this article that a pretty clear trends emerges in relation to the effectiveness of a variety of low-carbohydrate diets and their alternatives: there are evidence-based health benefits for a certain population and indirect benefits that support healthy weight loss; however, when calories are equated, low-carbohydrate diets are not inherently better for long-term fat loss. While it very well may be the case later on that such an approach is advantageous for weight loss as supported by the total body of literature, currently there is very little evidence to adopt a low-carb modality in order to optimize body composition.
Alternatively, there may even be some benefits to a higher-carb approach during a calorie-restricted period in order to maximize exercise performance and subsequently maintaining more muscle mass. The point here is that instead of rapidly jumping from diet to diet due to perceived claims of “magical” results, establish a nutritional plan that works best with your lifestyle and individual preferences. For most people, that’s a diet consisting of an appropriate amount of each macronutrient (protein, carbs and fats), along with plenty of other whole foods with sufficient vitamins and minerals. And yes, that includes carbs too.
With a bigger-picture approach, focus the majority of your attention during a dieting period towards a sustainable caloric deficit, regularly performing resistance training to maintain muscle mass, and eating a diet largely with the foods mentioned above that incorporates some flexibility with individual preferences. And above all, don’t fall into the traps and hype from “name-brand” diets that claim to be the best option, and when in doubt utilize nutritional strategies that have proven time and time again to be effective in scientific research.
- When total daily calories are equated, low-carb diets offer no inherent advantage for fat loss compared to a higher-carb approach.
- The main mechanisms by which popular low-carb regimens induce significant weight loss is largely due to appetite suppression and easier adherence for a specific population.
- Carbohydrates are actually particularly advantageous to dieters who practice strength sports- they help reduce performance degradations in the gym and retain more muscle mass during a calorie-restricted period.
- Keto, Carnivore, Paleo, Atkins and the Mediterranean diets may be beneficial towards certain individuals, however most people find them overly-restrictive and difficulty to remain adherent to over a long period of time.
- Time and time again, the best nutritional approach during a weight-loss period is consume foods that are both enjoyable and allow for the greatest amount of adherence.