For many people, improving health is a key motivator for losing excess body weight.
Achieving a healthy weight is associated with a lower risk of developing cardiometabolic health conditions such high blood pressure, Type 2 diabetes, heart disease, stroke, fatty liver disease and sleep apnea.
Clinically significant weight loss, defined as a loss of at least five per cent of initial body weight, has been shown to improve cardiometabolic risk factors such as waist circumference, blood pressure, blood cholesterol, blood glucose, insulin sensitivity and chronic inflammation.
A smaller weight loss – less than five per cent of initial weight – has also been shown to benefit a range of cardiometabolic health markers.
Now, a new study suggests that even in people who don’t lose weight, shifting to a healthy diet can result in notable cardiometabolic health improvements.
The findings add to convincing evidence that eating a high-quality diet offers substantial protection against chronic disease and premature death.
Here’s a look at the latest research – and why weight loss resistance should not deter you from following a healthy eating regime.
About the new analysis
For the study, published June 2 in the European Journal of Preventive Cardiology, researchers at the Harvard T.H. Chan School of Public Health and Ben-Gurion University of the Negev analyzed data from 761 participants with obesity who took part in three landmark long-term weight loss intervention trials conducted in Israel.
Participants were assigned to adopt and adhere to one of three diets – a low carbohydrate diet, a Mediterranean diet or a green-Mediterranean diet.
The low carbohydrate diet aimed to provide 20g of carbohydrates per day for the first two months, with a gradual increase to a maximum of 120g a day to maintain weight loss.
Both Mediterranean diets were calorie-restricted, plentiful in vegetables and low in red meat. They also included 28g of walnuts a day (e.g., 14 walnut halves).
The green-Mediterranean diet was higher in plant foods, especially ones rich in protective phytochemicals called polyphenols. The diet included three to four cups of green tea a day along with a green shake containing Mankai, a branded strain of an aquatic plant called duckweed (water lentils).
Participants were followed for 18 to 24 months to observe changes in weight and cardiometabolic risk factors including waist circumference, visceral fat (deep abdominal fat), liver enzymes, blood pressure, cholesterol, triglycerides, fasting glucose, insulin, inflammatory markers and leptin (a hormone that signals hunger).
The findings
During the study period, roughly one-third of participants (36 per cent) achieved clinically significant weight loss and another third lost between one and five per cent of their starting weight.
What stood out, though, was that 28 per cent of participants – despite closely adhering to their diets – did not lose any weight. “Weight-loss resistant” participants tended to be slightly older and more often women.
Participants who lost more than five per cent of their body weight experienced a variety of health improvements such as increased levels of “good” HDL cholesterol, reduced blood triglycerides, a decline in insulin, lower levels of leptin and a reduction in visceral fat.
Individuals who lost smaller amounts of weight also had marked improvements across many cardiometabolic risk factors.
Even among weight-loss resistant participants, eating a healthy diet resulted in important metabolic shifts, including a significant increase in HDL cholesterol, as well as reductions in leptin (leading to less hunger) and harmful visceral fat.
Across all three diets, the pattern of weight-loss resistance and metabolic improvements remained consistent.
A limitation of the study is the small number of women participating in the trials, limiting the ability to generalize the findings to females.
What causes weight-loss resistance?
It’s not well understood what causes weight-loss resistance, the inability to lose weight despite sticking carefully to plan. It’s thought that several interrelated factors may be involved.
Research suggests that some people may be better suited to a particular type of diet due to genetic variants that influence how the body metabolizes carbohydrates and fats.
Metabolic adaptation, when the body’s resting metabolism slows down in response to chronic low-calorie dieting, may also contribute to weight loss resistance.
Emerging evidence also suggests that the composition and function of the gut microbiome can influence an individual’s response to a weight loss intervention.
Takeaway
The new findings highlight the important benefits of following healthy diet, independent of weight loss, for protecting cardiometabolic health.
According to Dr. Iris Shai, principal investigator of the clinical trials and adjunct professor of nutrition at the Harvard T.H. Chan School of Public health, “This is more than a scientific insight – it’s a public health message. We must stop equating the scale with success. Everyone who embraces healthier habits deserves to know that their body is likely improving – even if the mirror doesn’t reflect it yet.”
Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan. Follow her on X @LeslieBeckRD
