Thanks to Atkins, Keto and the ‘no carbs before Marbs’ crews, low-carbohydrate diets have surged in popularity over the past couple of decades.
Low-carb diets promise faster weight loss, better blood sugar control, and improved energy. But do they live up to the hype, or are the claims overstated? At AdMac Fitness, we believe in evidence-based approaches, so here’s a balanced, neutral look at what high-quality research actually shows, highlighting both the benefits and the limitations.
What’s ‘Low’ Carb?
A “low-carb” diet typically means under 130 g of carbohydrates per day, while very-low-carb versions drop below 50 g. The ketogenic diet is essentially zero carb. These approaches replace carbs with more protein and/or fat, with the goal of putting the body in a state of ketosis.
Here’s what the science says as of 2026…
The Potential Benefits of Low Carb Diets
Whilst it might be tempting to look at diets through a vanity lens, we’ve got to look beyond that.
In this section, we’ll discuss the different health impacts of low-carb dieting, seeing where the true benefits lie for you. When you know the good and bad of the apporach, you’ll understand more about whether or not it’s right for you.
Weight loss
Several randomised trials and meta-analyses show that low-carb diets can produce meaningful short-term weight loss, often through reduced appetite and initial water loss.
A 2025 meta-analysis of randomised trials found carbohydrate-restricted diets led to greater reductions in body weight (−1.75 kg on average), BMI, fat mass, and waist circumference compared with higher-carbohydrate diets, with ketogenic versions showing the largest effects (−3.36 kg body weight). The study can be found here…
However, longer-term data tell a more nuanced story. ..
The landmark DIETFITS trial (Gardner et al., JAMA 2018) found no significant difference in 12-month weight loss between a healthy low-carb diet and a healthy low-fat diet (both groups lost around 5–6 kg on average). Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion.
Similarly, a 2022 Cochrane review of 61 trials concluded there is “probably little to no difference” in weight reduction up to two years compared with balanced-carbohydrate diets (moderate-certainty evidence). Low‐carbohydrate versus balanced‐carbohydrate diets for reducing weight and cardiovascular risk. In other words, low-carb can work well—but so can other sensible approaches when calories and food quality are controlled.
Type 2 diabetes management
This is where low-carb diets often shine. Multiple 2025 systematic reviews and meta-analyses confirm significant improvements in HbA1c and fasting glucose.
The standout long-term evidence comes from the Virta Health programme. This was a 5-year extension study (McKenzie et al., Diabetes Research and Clinical Practice, 2024) using a very-low-carb ketogenic approach with remote coaching. Among participants who completed five years:
Average weight loss of 8.8 kg (7.6 %)
HbA1c reduced by 0.3 %
20 % achieved full diabetes remission (HbA1c <6.5 % off all glucose-lowering medication)
Diabetes medication use dropped substantially (non-metformin meds fell from 56 % to 33 %)
Triglycerides fell 18 % and HDL cholesterol rose 17 %
These results are impressive and suggest that, with proper medical supervision and support, low-carb eating can help put type 2 diabetes into remission for some people.
Cardiometabolic improvements
Low-carb diets consistently lower triglycerides (often −15 mg/dL or more) and raise HDL (“good”) cholesterol, while also reducing blood pressure and inflammation markers in many trials. The same 2025 meta-analysis noted improvements in lipid ratios and overall cardiovascular risk scores. These are benefits that appear stronger with moderate low-carb approaches than extreme ketogenic versions.
The Potential Drawbacks of a Low-Carb Diet
So far, we’ve painted an overwhelmingly positive picture for low-carb diets, but we need to offer balance.
Here’s the other side of the low carb coin…
Not superior long-term for everyone
As noted in the Cochrane review and DIETFITS, any early edge in weight loss often disappears by one to two years. Adherence can be challenging—many studies show high dropout rates, and benefits tend to wane without ongoing support.
Cholesterol concerns
While triglycerides and HDL often improve, very-low-carb/ketogenic diets can raise LDL (“bad”) cholesterol and total cholesterol. The 2025 meta-analysis found ketogenic diets increased LDL by +13.3 mg/dL and total cholesterol by +13.8 mg/dL compared with moderate low-carb or balanced diets. For people already at higher cardiovascular risk, this may need close monitoring.
Nutrient shortfalls and side effects
Restricting whole grains, fruits, and some vegetables can reduce intake of fibre, certain vitamins (e.g., C, folate), and minerals. Reviews highlight the risk of deficiencies without careful planning or supplementation. Short-term side effects (“keto flu”—headaches, fatigue, constipation) are common when starting, though usually temporary.
Long-term data on gut health, bone density, and kidney function remain limited.
Not one-size-fits-all
Low-carb diets may not suit athletes needing quick energy, people with certain medical conditions (e.g., kidney disease), or those who simply prefer higher-carb eating patterns. Evidence also shows that diet quality matters enormously—plant-based low-carb versions tend to fare better for long-term health than those heavy in processed meats and saturated fats.
The Bottom Line
The evidence is clear: low-carb diets are not magic, but they can be an effective tool for some people, particularly those with type 2 diabetes or insulin resistance.
When done thoughtfully and with professional guidance, they often deliver short-term wins on weight, blood sugar, and certain heart-health markers, yet they are not superior to other balanced approaches for long-term weight loss in the general population, and they come with trade-offs around LDL cholesterol, nutrients, and sustainability.
At AdMac Fitness, we don’t push any single diet. Instead, we help clients find what fits their lifestyle, goals, and blood work. Many members combine a moderate low-carb approach with our Small Group Training to preserve muscle mass, boost metabolism, and make the changes stick.
If you’re curious about trying low-carb, speak to your GP or a registered dietitian first, especially if you take medications for diabetes or blood pressure. And if you want support with workouts that complement your nutrition plan, our doors (and coaches) are always open.
Want to improve your health and fitness? Let the AdMac Fitness Personal Trainers help…
AdMac Fitness has been helping the people of East London transform their health and fitness for nearly a decade.
We help people using tried and tested fitness approaches. Our expert team of personal trainers, based in both Bow and South Woodford can help you get a grip of your health forever. With our guidance and experience, you can relax knowing that your fitness journey is going to be guided by some of the best personal trainers in East London.
For more information on who we are, what we do and how we can help you achieve your health and fitness goals, contact us on… 07921465108 or email us at admacfitness@gmail.com. We look forward to hearing from you!
Our locations are…
AdMac Fitness: Arch 457 Robeson St, London E3 4JA
AdMac Fitness South Woodford: Unit 4 Marlborough Business Centre, 96 George Lane, South Woodford, London, E18 1AD