Frustrated with weight loss attempts? Confused on which diet to try, and which one is the “best” and not just a fad? In this post, we are going to talk about the core components of diets, and how they compare to one another over the span of 6 months to 2 years. Rest assured, the information listed below is backed by randomized controlled trials, meta-analyses, and systemic reviews. Meaning? The medical literature is vast when it comes to diets and weight loss.
The three macronutrients in all diets include Carbohydrates, Protein, and Fat.
9 calories= 1g of fat
4 calories = 1g of protein
4 calories = 1g of carbohydrate
Listed below are three articles addressing diets with different macronutrient compositions. Some of the studies evaluated participants for 6-12 months, while another was able to capture participation for as long as two years.
Macronutrient Diet Comparisons < 1 year
The table below lists three main categories of diet types: low carbohydrate, moderate macronutrients, and low fat. Within each of these categories, multiple popular brands were reviewed in a systemic review completed in 2014. The macronutrients were each broken down into % of calories in one day. Weight loss was recorded at 6 months and again at 12 months.
|Diet Type||Brands||% Carbs|
(of total calories)
(of total calories)
(of total calories)
|6 Months||12 Months|
|< 40%||30%||30-55%||↓ 19 lbs||↓16 lbs|
|Moderate Macronutrients||Biggest Loser|
|55-60%||15%||23 - < 30%||↓ 16 lbs||↓ 10 lbs|
|60%||10-15%||< 20%||↓ 18 lbs||↓ 16 lbs|
When the individual diets were compared to each other, the overall difference in weight loss was small. Therefore, when attempting to make a specific recommendation about one diet over another, there is inadequate evidence in the medical literature to recommend one particular (branded) diet.1
Any diet is better than no diet, as long as you enjoy the diet and adhere to it for as long as possible.
Low Fat vs. High Fat Diets = 1 year
A meta-analysis and systemic review was conducted on 53 randomized controlled studies (including 68,000+ participants!) looking at long-term effects of low-fat diets vs. high-fat diets. Previously, the theory behind low-fat diets was that it reduces the overall intake of calories, since fat offers more calories gram for gram when compared to protein and carbohydrates. However:
…randomized controlled studies have failed to consistently demonstrate that reducing the percent of energy from total fat leads to long-term weight loss compared to other dietary interventions.” 3
The “low-fat diet” group in this article ranged from < 10% fat calories (of total daily diet) to < 30%. The comparison “high-fat diet” groups included diets considered low-carb and moderate-to-high fat.
Regarding weight loss, higher fat and low-carbohydrate diets led to significantly greater weight loss than low-fat interventions.
Macronutrient Diet Comparisons = 2 years
In a study published in the 2008 New England Journal of Medicine, ~300 patients were assigned to one of the three diets: low carb, Mediterranean, or low fat2. The average patient was a 52 year old male with a BMI* of 31. At the end of the 2 years, the adherence rate was 85%.
All participants- regardless of diet- had significant decreases in waist circumference, blood pressure, and improvements in cholesterol (with an increase in HDL cholesterol- “good” cholesterol).
Those participating in the Mediterranean diet had the best improvement in fasting blood glucose and insulin levels.
*BMI = body mass index (weight in Kg / square of the height in meters)
|Low Carb||Unrestricted||< 40% of diet. Highest urine ketones.||20% of diet||40% of diet. Highest intake of total and saturated fat.||Highest intake of cholesterol. Total cholesterol and HDL improvement by 20%. Decrease in triglycerides|
|Mediterranean||1500 cal Women|
1800 cal Men
|50% of diet. Highest intake of dietary fiber||20% of diet||30% of diet. Highest in monounsaturated fat|
|Low Fat||1500 cal Women|
1800 cal Men
|50% of diet||20% of diet||30% of diet. [10% saturated fat]||Intake = 300mg / day. Total cholesterol and HDL improvement by 12%|
Description of diets used in the study:
- Low Carb = 20g / day x 2 months with a gradual increase to 120g / day to maintain weight loss. Vegetable sources of fat and protein were emphasized with avoidance of trans fat.
- Average weight loss @ 2 years = 12 lbs
- Mediterranean = rich in vegetables, low in red meat. Poultry and fish were eaten instead of beef and lamb. Fat sources included 30-45g of olive oil and a handful of nuts (5-7 nuts = <20g / day).
- Average weight loss @ 2 years = 10 lbs
- Low Fat = low-fat grains, vegetables, fruits, and legumes. Limited consumption of additional fats, sweets, and high-fat snacks.
- Average weight loss @ 2 years = 7 lbs
The Mediterranean Diet and low carbohydrate diets may be more effective than low fat diets if maintained over the long-haul in terms of average weight lost*.
*>80% of participants were men; a significant limitation of this study.
- For those with high total cholesterol or low HDL cholesterol, a low carbohydrate diet may be of benefit.
- For those with diabetes or blood sugar issues, the Mediterranean diet may be a preferred diet option
Regardless of which diet you choose to participate in, always ensure you are nourishing your body with clean, minimally processed, high quality foods. Avoid foods artificially treated with chemicals and preservatives, and eliminate sugar-sweetened beverages whenever possible. Aim for USDA organic and non-GMO options if feasible, and make a goal of hitting at least 64oz of water daily to stay hydrated and prevent kidney stones. 🙂
When you’re hungry, reach for foods rich in protein or fats before carbohydrates, such as (white > red) meats, seafood, nuts, eggs, and oils (ie: coconut, olive oil). When reaching for carbohydrates, stick to non-starchy vegetables first (ie: lettuce, tomatoes, cucumbers etc.) before starchy vegetables (ie: potatoes, yams) and fruit (especially dried fruit!). As always, listen to your body and do what feels healthy and good for you.
Better yet, enhanced weight loss can occur with behavioral support and the addition of exercise. Get moving!
Hungry for more information on Diets?
Check out these other blog posts:
- Johnston, Bradley C., et al. “Comparison of Weight Loss Among Named Diet Programs in Overweight and Obese Adults.” JAMA, vol. 312, no. 9, 2014, pp. 923–933., doi:10.1001/jama.2014.10397.
- Shai, Iris, et al. “Weight Loss with a Low-Carbohydrate, Mediterranean, or Low-Fat Diet.” New England Journal of Medicine, vol. 359, no. 3, 17 July 2008, pp. 229–241., doi:10.1056/nejmc081747.
- Tobias, Deirdre K, et al. “Effect of Low-Fat Diet Interventions Versus Other Diet Interventions on Long-Term Weight Change in Adults: A Systematic Review and Meta-Analysis.” The Lancet Diabetes & Endocrinology, vol. 3, no. 12, Dec. 2015, pp. 968–979., doi:10.1016/s2213-8587(15)00367-8.