Yo-yos are inexpensive kids’ toys that seem to defy gravity. But when the yo-yo’s movement describes how many people gain weight and then lose weight and then gain again, it’s no fun. Constantly gaining and losing weight, known to the public as “yo-yo” dieting, remains harmful.
However, researchers at Ben-Gurion University of the Negev (BGU) in Beersheba have discovered that losing weight by healthful eating over 18 months and then gradually gaining weight confers long-term health benefits. These cycles may affect not only body weight, but also body composition, particularly visceral (intra-abdominal) fat – a metabolically active tissue linked to cardiometabolic disease.
The study’s principal investigator is Prof. Iris Shai, who is dean of the School of Sustainability at Reichman University in Herzliya, an adjunct professor at the Harvard TH Chan School of Public Health, and an honorary professor at Leipzig University, Germany. She said that these findings challenge the traditional focus on weight loss as a simple numbers game.
She told The Jerusalem Post in an interview that the entire study – the largest long-term MRI-based repeated weight-loss trials – was conducted solely at the Shimon Peres Negev Nuclear Research Center (sometimes unofficially referred to as the Dimona reactor) because the staff spend a long time there eating meals and remain employed there for long periods.
The work was carried out by experts at BGU, together with researchers from Harvard, Leipzig, and Tulane University in Louisiana, in collaboration with the Briuta Medical Center and Soroka-University Medical Center, both in Beersheba.
The specifics of the study
The researchers conducted the first lifestyle weight-loss randomized controlled dietary trials (DIRECT-PLUS and CENTRAL) on the Dimona employees in 2012-14 and the second one in 2017-18. Each trial lasted 18 months and included 300 participants (a third of the participants in the first trial also took part in the second trial).
All participants were invited for follow-up in 2022-2024 to assess weight, metabolic biomarkers, and fat deposits in MRI scans five years after the second trial.
The trials examined participants who followed the Mediterranean or green-MED diets based on the traditional, plant-dominant diets of Greece, Italy, and Spain. It includes vegetables, fruits, whole grains, beans, nuts, and extra virgin olive oil as the primary fat source; fish is eaten regularly, while poultry, dairy, and eggs are consumed in moderation.
In the Green-MED diet, they consumed more “greens” as green tea and mankai and omitted meat. Mankai is a highly nutritious, iron-rich, and protein-packed strain of Wolffia globosa (duckweed) marketed as a sustainable “superfood” green vegetable. It contains iron, vitamin B12, fiber, and omega-3s, showing potential in reducing blood sugar and fat. It is often used frozen in smoothies or as a nutrient boost. The study participants also exercised.
This group was compared with a control diet having the same intensity and calories. Detailed MRI scans were carried out before and after each intervention, five times on each participant, so the team could study their visceral fat and not base their conclusions just on their body mass index (BMI).
The study found that, surprisingly, although participants entered the second intervention at a body weight similar to what they had at the start of the first one – indicating that they had regained all the weight they had lose – their abdominal fat profile and metabolic markers were more favorable, with improvements of approximately 15%-25% compared to their initial baseline, including enhanced insulin sensitivity and a more favorable lipid profile.
Those whose weight seesawed over this long period were healthier than those who tried to lose weight without observing healthful habits. “Our message is that over a long period, observing lifestyle changes, even if one gained weight, is better than just trying to lose weight, even if it’s harder in the second bout – don’t give up! Shai declared.
“So, for many people, the key question is not whether to lose weight once, but whether repeated attempts confer long-term health benefits or risks.”
She said that persistent commitment to a healthy dietary change creates cardiometabolic memory in the body.
“Repeated participation in a lifestyle program aimed at weight loss, even after an apparent ‘failure’ in which an individual regains all the weight lost in a previous diet, may lead to significant and sustainable health benefits over the years, particularly through the reduction of harmful visceral fat.”
BGU doctoral student Hadar Klein, a registered dietitian who was the lead author, added that “body weight alone does not capture changes in visceral fat or metabolic biomarkers. Even when weight is regained, cardiometabolic health may remain improved, and success should not be defined solely by the number on the scale.
Importantly, even when weight loss is attenuated during a second attempt, the cumulative benefits for abdominal fat and metabolic health are substantial.”
The study has just been published in BMC Medicine under the title “How effective is rejoining a long-term weight loss program? The 5- and 10-year MRI-assessed Follow Interventions Trial (FIT) project.”
This finding points to the existence of a positive “cardiometabolic memory” from prior intervention that persists even after weight regain. In addition, although participants who rejoined the weight-loss program lost less weight during the second intervention, they maintained better long-term health outcomes.
Five years after completing the second intervention, these participants showed less weight regain and less accumulation of abdominal fat compared with participants who had engaged in a weight-loss program only once.
“Despite an attenuated weight-loss response, repeated engagement in a structured lifestyle intervention yields meaningful long-term impacts with sustainable metabolic benefits,” the researchers concluded. “Despite a reduced reaction of weight loss, the fact that they continued to follow a structured lifestyle intervention brings about meaningful long-term impacts with sustainable metabolic benefits.”