Low-carbohydrate diets, commonly known as low-carb diets, have been advertised as a “guaranteed strategy” for weight loss by social media influencers and media. The popular idea behind this strategy is that by eliminating almost all sources of carbohydrates, including fruits, grains, potatoes, rice and bakery products, the body should make an immediate switch from burning glucose to burning fat for energy.
This should naturally lead to achieving that desired figure once and for all. But is that really what happens? How successful are low-carb diets for weight loss in the short term and the long term? What does the research say?
Let’s find out.
Obesity, or being overweight, has become a major public health problem. In the UK, the average adult consumes up to 300 calories [1] above the recommended daily intake. Over time, this may become a significant issue and a source of ill health. Managing the health consequences of chronic obesity presents a concerning challenge to UK healthcare services, [2] costing around £6.2 billion per year on surgical procedures, medications, and emergency response.
If obesity trends continue increasing, the implications for public health funding risk over-stretching an already under-resourced national health service (NHS). Carrying excess body weight in the form of fat mass predisposes us to an increased risk of numerous chronic diseases such as cancer, diabetes, immunological problems and cardiovascular disease [3].
Eager to find practical, cost-efficient solutions, scientists globally have been exploring diverse dietary strategies to address the problem. One such strategy that has captured media attention is the restriction of dietary carbohydrates, commonly known as the "low-carb diet" (LC).
What are carbohydrates?
Let’s take a minute to explore this (often misunderstood) question. Carbohydrates are one of the 3 macronutrients (energy-providing nutrients), along with fats and protein, in foods. [4] They are the preferred energy source for our body and brain, delivering 4 calories per gram.
Not all carbohydrates are equal.
Simple Carbohydrates such as glucose, fructose or a little bit more complex sucrose (table sugar) have only one or two sugar molecules that are quickly and easily digested and absorbed by our body. Simple carbohydrates are abundant in fruit, berries, honey, milk and dairy products as well as candy and sweets.
Complex carbohydrates, such as those found in potatoes and grains, are made of lots of sugar molecules that take longer to digest and absorb into our bloodstream. They provide a lot of caloric energy, though some types are also forms of dietary fibre, which we are unable to digest.
What is a low-carbohydrate diet? (LC)
LC diets are essentially characterised by their restriction of carbohydrates from foods such as potatoes, grains, pasta, rice, fruits, and sometimes even vegetables. People following these diets obtain the majority of their calories from fats (oils, fish, avocados, nuts, seeds, eggs) and protein-rich foods such as lean & red meats, seafood, tofu and dairy products.
LC diets come in many shapes and sizes. And while the individual definitions and cut-offs remain somewhat blurry, in research [5], four levels are generally recognised according to the proportion of carbohydrates from total calories consumed.
High-Carb (45%+)
Moderate-Carb (26% - 44%)
Low-Carb (< 26% )
Very-Low Carb ( < 10%)
How much weight do people lose on low-carb diets?
This topic has been the focus of extensive research for quite some time. A meta-analysis, a study type that consolidates and interprets data from multiple investigations, was conducted in 2022 [6]. In this comprehensive review, scientists examined 25 studies comparing low-carbohydrate diets to balanced diets, which contain 40-60% carbohydrates, in the context of weight loss.
Here are their findings:
In the short term, people following the LC diet are losing more weight and losing it faster.
At the 3-4 month mark, people on low-carb diets were 2.6 kilos ahead of their moderate-carb counterparts.
At the 6-8 month mark, the advantage of LC increases to an additional 2.7 kilos.
Let’s take a look from another perspective.
There is a crucial factor in weight loss studies, which often tends to go overlooked: caloric control. Are researchers merely restricting the type of food people eat (e.g. low carb, low fat, etc.), or are they also restricting total calories? That’s a significant difference.
The above 2022 analysis did not control for total calories. In other words, we cannot be certain if the rapid weight loss resulting from low-carb diets stemmed from carbohydrate restriction or caloric reduction. You could be eating only 2000 calories of M&Ms a day and still lose weight if your caloric requirement is 2500 calories (of course, there would be other consequences).
Are people on LC diets losing weight because they are eating less?
2022 review of randomised controlled trials [7] looked into this. This is what they found at 3-12 month mark.
Where total calories were matched between LC and moderate-carb groups, there was almost no difference in the amount of weight lost.
Where the LC group were told to eat as much as they could, and the moderate-carb group had their calories moderated, LC lost 2 extra kilos.
Where all caloric instructions were deliberately left out, and people were only told to go low-carb or moderate-carb without receiving any instructions on calories, the LC group lost nearly 3 kilos more, on average.
This is a very compelling finding. It suggests that regardless of whether calories are restricted or not, low-carbohydrate diets seem to be superior to moderate-carbohydrate intakes for weight loss. At least within the 3-12 months bracket.
But most people who are losing weight are looking for a long-term solution rather than a short-term yo-yo diet. Can the LC diet stand strong even in the face of long-term studies? Let’s find out.
Is a low-carbohydrate diet effective for weight loss in the long term?
Within the first 12 months of dieting, LC takes the lead, as demonstrated above. However, passing the 12-month “dieting anniversary”, the weight-loss dynamic begins to change. While those following LC diets continue losing weight, those in balanced-carb groups are slowly catching up.
According to the meta-analysis [7] by the Cochrane Collaboration (the gold standard in nutritional research), after the first year, the LC group's lead shrinks to less than 1 kilogram ahead, compared to those following the moderate-carb approach. This difference diminishes as studies continue, eventually disappearing altogether.
Furthermore, in studies that have lasted over 24 months, the moderate carbohydrate approach is starting to take the lead and dominate over the LC groups. In addition, those in the moderate-carb approach have, overall, seen an improvement in their “good” HDL-cholesterol compared to low-carb. This is a very positive finding and one which I will explore in a future article.
Bottom Line:
In the short term (3-12 months) LC diets are more effective at weight loss than diets with a more balanced carbohydrate profile.
In the long-term (> 12 months), people following a LC diet achieve a similar amount of lost weight to those eating moderate carbohydrate diets.
Why do people on low-carb diets lose weight so quickly?
The exact reason behind this isn't completely clear, but it's probably due to a mix of different factors.
Many people transition to a low-carb diet from a traditional Western diet filled with processed carbs and calorie-dense foods. Making this switch to a more nutritionally sound and low-carb diet will naturally result in weight loss as people subconsciously tend to reduce the amount of calories they consume.
Diets restricting carbohydrates tend to be richer in protein and fat with a higher satiation index, reducing the desire to eat more. [8]
Low-carb diets have been demonstrated to regulate blood levels of specific hormones that signal hunger [9]
Low-carb diets may lead to the depletion of muscle glycogen [10], our body’s storage form of glucose, which causes the loss of the additional water required to retain glycogen.
Why does the effectiveness of low-carb diets slow down in the long run?
The phenomenon known as metabolic adaptation [11], adding another layer to the weight loss puzzle, might be part of the explanation. Though not fully understood, it suggests that initial weight loss often hits a plateau due to a mix of genetic adaptations, hormonal shifts, and changes in non-exercise activity thermogenesis (NEAT). Historically, rapid weight loss would signal an emergency in the human body, triggering metabolic changes to conserve energy. This may partly explain why long-term weight loss becomes more challenging.
It's essential to think about motivation and how sustainable a diet is for long-term success. Many people struggle to stick to a new diet because they lose interest or find it too limiting. Consider the role of food in various cultures; dishes from India, Morocco, France, the UK, Mexico, and Japan often have higher carb content. Being too restrictive could make your diet less enjoyable and harder to maintain in the long run.
Bottom Line:
In the short term, LC diets often work by depleting glycogen, which leads to loss of water. These diets tend to be higher in protein, which also improves satiety.
Over time, their effectiveness may decline due to metabolic changes and waning motivation or enjoyment of the diet.
How can I eat healthier carbohydrates?
Instead of restricting carbohydrates, improving the quality and moderating the quantity to around 45-60% of total calories might be the most effective way to manage your weight in the longer term.
The Mediterranean diet, for instance, is associated with numerous health benefits and is supported by an abundance of research, and includes a similar proportion of calories from healthy carbohydrate sources like wholegrains, fruits and vegetables. These benefits include improved cholesterol levels, a healthier body weight, and reduced risk of chronic illnesses like cancer and diabetes. Additionally, it may even provide added defence against cognitive decline and dementia. [12]
“Sounds good, so how do I start?”
Aiming to eat carbohydrates in their most natural form is a good start. Many of the carbohydrates we commonly consume, such as pastries, white rice or breakfast cereals, are primarily made from refined wheat or corn flour. Whole grains like wheat, corn, and rye are healthy in their natural state. However, the refining process—especially when sugar and butter are added—can make them less nutritious and more problematic when eaten in excess. This has led to a negative perception of carbohydrates as a whole. However, as you may now appreciate, not all carbs are equal.
Try this
Opting for whole-food carbohydrate alternatives can make a significant difference when trying to lose weight. Try downloading my 5-step visual guide to get started.
Is weight loss a constant struggle for you?
Maybe you feel like you’ve been dieting on and off for most of your life. Yet, despite giving it your best, time and time again, you are still far from where you want to be. I get you. I’ve gone through something similar.
In its essence, weight loss is simply burning more calories than consuming. But the foundation of sustainable and long-term weight loss strategy is so much more than that. It involves creating a certain type of lifestyle and building certain habits that will prevent that weight from coming back.
A mindset shift has to happen as well. The way you see yourself, your body and your identity. A lot of what we are being taught about body image is incredibly toxic and dysfunctional. Unwiring a lot of common beliefs about weight loss is essential for healthy weight loss.
And finally, numerous weight loss diets are nothing else than short-term gimmicks potentially jeopardising your long-term health, leading to bone loss, muscle loss and even loss of menstrual cycle in women.
What I would like to offer you is a sustainable, ethical and evidence-based approach. I do not guarantee immediate results or 30-day money back. What I can guarantee is that you are not going to destroy your health following this approach!
So if that resonates, consider booking a free call with me by following this link.
Take the first step towards a better future.
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References
[1] Tackling obesity: empowering adults and children to live healthier lives, Department of Health & Social Care , Available at: https://www.gov.uk/government/publications/tackling-obesity-government-strategy/tackling-obesity-empowering-adults-and-children-to-live-healthier-lives
[2] Statistics on Obesity, Physical Activity and Diet, England, 2020, NHS Digital, Available at: https://digital.nhs.uk/data-and-information/publications/statistical/statistics-on-obesity-physical-activity-and-diet/england-2020/part-3-adult-obesity-copy
[3] Obesity and Comorbid Conditions, National Library of Medicine, StatPearls Available at: https://www.ncbi.nlm.nih.gov/books/NBK574535
[4] Physiology, Carbohydrates, StatPearls (2023). Available at: https://www.ncbi.nlm.nih.gov/books/NBK459280/
[5] Low-Carbohydrate Diet, StatPearls (2023). Available at: https://www.ncbi.nlm.nih.gov/books/NBK537084/
[6] Silverii, Giovanni Antonio et al. “Effectiveness of low-carbohydrate diets for long-term weight loss in obese individuals: A meta-analysis of randomized controlled trials.” Diabetes, obesity & metabolism vol. 24,8 (2022): 1458-1468. doi:10.1111/dom.14709
[7] Naude, Celeste E et al. “Low-carbohydrate versus balanced-carbohydrate diets for reducing weight and cardiovascular risk.” The Cochrane database of systematic reviews vol. 1,1 CD013334. 28 Jan. 2022, doi:10.1002/14651858.CD013334.pub2
[8] Martin, Corby K et al. “Change in food cravings, food preferences, and appetite during a low-carbohydrate and low-fat diet.” Obesity (Silver Spring, Md.) vol. 19,10 (2011): 1963-70. doi:10.1038/oby.2011.62
[9] Sumithran, P et al. “Ketosis and appetite-mediating nutrients and hormones after weight loss.” European journal of clinical nutrition vol. 67,7 (2013): 759-64. doi:10.1038/ejcn.2013.90
[10] Barber TM, Hanson P, Kabisch S, Pfeiffer AFH, Weickert MO. The Low-Carbohydrate Diet: Short-Term Metabolic Efficacy Versus Longer-Term Limitations. Nutrients. 2021 Apr 3;13(4):1187. doi: 10.3390/nu13041187. PMID: 33916669; PMCID: PMC8066770.
[11] Martínez-Gómez, Mario G, and Brandon M Roberts. “Metabolic Adaptations to Weight Loss: A Brief Review.” Journal of strength and conditioning research vol. 36,10 (2022): 2970-2981. doi:10.1519/JSC.0000000000003991
[12] Mediterranean Diet, StatPearls, (2023). Available at: https://www.ncbi.nlm.nih.gov/books/NBK557733/