In the 1970s, low-carbohydrate diets were the norm. Carbohydrates are found in bread, grains, fruits, vegetables, and milk, and they are also present in highly processed fast foods, cakes, potato chips, and sodas. Nowadays, low-carbohydrate meals are promoted as solutions for weight loss, overcoming heart diseases, and being better alternatives for diabetes. But how do these claims align with the latest research? A new evidence review found that long-term followers of low-carbohydrate diets lost just under one kilogram (about 2 pounds) more weight than those on other diets. However, the review concluded that there is no evidence that low-carbohydrate diets offer any additional health benefits. In fact, if you are following a low-carbohydrate diet, you will need to pay more attention to what you eat to ensure you get enough vitamins, minerals, dietary fiber, and other phytonutrients.
The Cochrane review included 61 randomized controlled trials (the highest level of evidence) with nearly 7,000 overweight adults, around 1,800 of whom had type 2 diabetes. People within a healthy weight range were not included. The reviewers compared various weight loss diets based on carbohydrate content:
1. Low-carbohydrate diets: This included low-carbohydrate or ketogenic diets (less than 50 grams of carbohydrates per day or less than 10% of your total energy from carbohydrates), and low-carbohydrate meals (50-150 grams of carbohydrates per day or less than 45% of your total energy from carbohydrates).
2. Balanced carbohydrate diets (more than 150 grams of carbohydrates per day or 45-65% of your total energy from carbohydrates).
They found that among overweight adults (but not those with type 2 diabetes), those following a low-carbohydrate diet for 3 to 8.5 months lost, on average, one kilogram more than those on a balanced carbohydrate diet. However, when they ensured that energy intake restrictions were the same in both groups by providing food or meal plans, the difference was about half a kilogram. In long-term weight loss interventions lasting from one to two years, the average weight loss difference between those on low-carbohydrate diets versus balanced carbohydrate diets was just under one kilogram.
The average weight loss varied significantly across different diets, ranging from less than one kilogram in some to about 13 kilograms (28 pounds) in others. Studies on adults with type 2 diabetes showed greater initial weight loss on low-carbohydrate diets compared to balanced carbohydrate diets: 1.3 kg over three to six months. However, in longer interventions lasting between one to two years, there was no difference. In the small group of studies that included a follow-up period after the weight loss intervention, there were no differences in weight loss among adults with or without type 2 diabetes.
There were no statistically significant differences in other health measures, such as blood pressure, cholesterol, blood sugar control, or risk of constipation. They found no clinically significant differences in outcomes based on the level of carbohydrate restriction among participants. Overall, the review indicates that whether you prefer a low-carbohydrate eating pattern or a balanced carbohydrate diet, both can be effective for weight loss.
### Nutrients to Monitor on a Low-Carbohydrate Diet
Your body uses carbohydrates as a macronutrient to produce energy for muscle function, brain activity, lungs, and other vital processes. Healthy foods containing carbohydrates—such as bread, grains, fruits, vegetables, and milk—are rich in other essential nutrients, especially dietary fiber, thiamine, calcium, and folic acid. Without careful planning, a low-carbohydrate diet can also be lower in these nutrients. So how can you ensure you are consuming enough? Here’s what to look for and some low and high carbohydrate options.
- **Dietary fiber**: Essential for maintaining regular bowel function and promoting healthy bacteria growth in the colon.
- Low carbohydrate sources: spinach, fresh berries, almonds, cauliflower.
- High carbohydrate sources: whole grains, apples, chickpeas, sweet potatoes.
- **Thiamine (Vitamin B1)**: Necessary for providing energy to body tissues and used in carbohydrate metabolism.
- Low carbohydrate sources: tuna, sunflower seeds, beef, yeast extracts.
- High carbohydrate sources: brown rice, black beans, whole grain bread, yogurt.
- **Calcium**: Essential for strong bones.
- Low carbohydrate sources: hard cheese, canned salmon, almonds, firm tofu.
- High carbohydrate sources: yogurt, milk, soft cheese.
- **Folic acid**: Crucial for growth and used in DNA synthesis, your genetic blueprint. Adequate intake is particularly important for women as folic acid is essential for preventing neural tube defects in babies during pregnancy.
- Low carbohydrate sources: leafy green vegetables, avocados, broccoli, peanuts.
- High carbohydrate sources: whole wheat bread, fortified whole grain cereals, brown rice, oranges.
In conclusion, if you love carbohydrates and want to lose weight, you can do so. Plan to reduce your carbohydrate intake by avoiding ultra-processed, energy-dense, and nutrient-poor foods (unwanted foods) while continuing to consume carbohydrates from healthy foods. The report was prepared with the collaboration of Claire Collins, Emeritus Professor of Nutrition and Dietetics, Erin Clarke, Postdoctoral Researcher, and Rebecca Williams, Postdoctoral Researcher, from the University of Newcastle.
