I usually counsel my patients that the best diet for weight loss is not really a “diet,” but rather a healthy approach to eating that makes them feel good and that is good for their body.
I love when the research supports my advice, as did results from the SWIFT (Support strategies for Whole-food diets, Intermittent Fasting and Training) study.
Study looks at three popular diets
The SWIFT study of 250 overweight adults was intended to compare different types of weight loss support (daily self-weighing, regular phone calls, hunger training, or dietary self-monitoring) using the Mediterranean diet, paleo diet, or intermittent fasting (IF). A side study, published in the American Journal of Clinical Nutrition, specifically looked at adherence and outcomes (weight, waist circumference, blood pressure, blood sugar, cholesterol, and inflammation level) of these diets after 12 months.
Participants were allowed to choose their diet, and most (54.4%) chose IF; 27.2% chose the Mediterranean diet; and 18.4% chose the paleo diet. Participants were randomly and evenly assigned to one of the four different weight loss supports only after they chose their preferred diet. In addition, they all received 30 minutes of one-on-one education and written resources specific to whatever diet they chose, as well as a more general pamphlet describing behavioral strategies for weight loss, including tips on everything from food shopping to stress management to sleep and exercise.
Those choosing IF followed the 5:2 protocol, which means drastically reducing food intake for any two of five days of the week (down to 500 calories for women and 700 calories for men). The Mediterranean dieters emphasized fruits and vegetables, legumes, nuts, seeds, whole grains, and olive oil with moderate fish, chicken, eggs, and dairy, and with an allowance of one glass of wine per day for women and two per day for men. The paleo diet emphasized fruits and vegetables, animal proteins, coconut products, butter, and olive oil, along with some nuts, seeds, and legumes.
Some diets may be easier to stick to than others
After 12 months, more participants were able to stick with the Mediterranean diet (57%) and IF (54%) than the paleo diet (35%). Even with the imperfect adherence to any one diet, everyone lost weight (an average of 6.2 pounds with the Mediterranean diet, 8.8 pounds with IF, and 4 pounds with the paleo diet). Those who stuck with their diet lost an average of one to three pounds more.
Some diets had other benefits as well. Those in the Mediterranean diet and IF groups enjoyed significant drops in blood pressures, and those in the Mediterranean diet group also had a significant, healthy drop in blood sugars.
This study was not perfect. You could argue, as these authors do, that the fact that participants chose their preferred diet is a good thing, as it could theoretically improve adherence. However, it also resulted in very different-sized groups to start with. The varying adherence and exercise option choices were adjusted for as well as possible. And the study relied heavily on self-reporting, which is always iffy.
Healthy eating patterns have benefits beyond weight loss
But we can still learn a great deal here. The Mediterranean approach to eating (which can be easily modified to suit any country or cultural food preferences) has mountains of research behind it. This is the dietary approach that is the most well-studied, and it is associated with lower risks for diabetes, high blood pressure, heart disease, strokes, dementia, cancer, and other ailments. The lower blood pressures and blood sugars seen in this study further support previous findings.
IF is a newer approach that is just now becoming better studied, and the emerging evidence is encouraging. IF makes intuitive and physiologic sense, and is relatively easy (certainly uncomplicated) to incorporate into day-to-day life, with potential positive health effects beyond weight loss. The timing of the fast can be adjusted for individual preferences and schedules. For example, the 16:8 IF protocol calls for completing the last meal by 7 pm and not eating again until at least 11 am the next day. This works well for folks like me who are happy with just a coffee in the morning. Others may prefer to eat at 7 am and fast after 3 pm, which is fine as well.
The paleo diet was the least successful diet in this study. Any eating approach that completely eliminates entire large food groups such as grains, and instead emphasizes meat and animal products, is going to be more difficult to follow, more expensive, and more likely to cause heart disease.
The bottom line
In summary, the best diet for weight loss is not a diet at all, but rather a healthy approach to eating that you can adopt for life. My suggestion is to try combining a whole-foods, plant-based eating approach (like the Mediterranean diet) with some form of IF. Enjoy celebrations, be active, manage stress, and get enough sleep.