Everything we know about losing and gaining weight may be wrong.

A new systematic review published in the peer-reviewed American Heart Association journal, Circulation: Cardiovascular Quality and Outcomes, has found that losing weight through an intensive behavioral weight loss program can reduce the risk factors for cardiovascular disease and type 2 diabetes for at least five years, even if some weight is regained.

The review demonstrates that the heart health benefits of weight loss through lifestyle changes persist over time.

According to the American Heart Association’s 2023 Statistical Update, people who are overweight or affected by obesity are at a greater risk of developing high cholesterol, high blood pressure, insulin resistance, and cardiovascular disease. Globally, 2.4 million deaths in 2020 were attributed to being overweight and obese.

Behavioral weight loss programs can be effective in promoting weight loss and healthy habits, such as eating nutritious foods and engaging in physical activity. Although regaining some weight after such programs is common, some observational studies have suggested that this pattern of weight loss followed by weight regain may increase cardiovascular risk. However, the authors of this analysis caution that randomized trials and long-term follow-up studies are needed to better understand this association.

“Many doctors and patients recognize that weight loss is often followed by weight regain, and they fear that this renders an attempt to lose weight pointless,” adds study co-senior author Susan A. Jebb. “This concept has become a barrier to offering support to people to lose weight. For people with overweight or obesity issues, losing weight is an effective way to reduce the risk of Type 2 diabetes and cardiovascular disease.”

The review analyzed scientific studies from 2018 to compare risk factors for cardiovascular disease and Type 2 diabetes between individuals who underwent an intensive behavioral weight loss program and those who followed a less intensive or no weight loss program. The studies in the analysis utilized interventions such as diet and/or exercise, partial or total meal replacement, intermittent fasting, or financial incentives contingent on weight loss. The studies were conducted in various settings and modes of delivery (in-person, app-based, telephone, etc.).

The review included 124 studies involving over 50,000 participants, with an average follow-up of 28 months. The results of these studies were combined to estimate changes in risk factors for cardiovascular disease and Type 2 diabetes after weight loss. The average weight loss ranged from 2-5 kilograms (5-10 pounds), and weight regains averaged 0.12 to 0.32 kg (0.26 pounds to 0.7 pounds) per year. Participants had an average age of 51 years old and a body mass index of 33, indicating obesity.

According to the analysis, compared to those in less intensive or no weight loss programs, participants who lost weight through an intensive program had lower risk factors for cardiovascular disease and Type 2 diabetes. The pooled results of the studies showed that on average:

• Systolic blood pressure, the top number in a blood pressure reading, was 1.5 mm Hg (millimeters of mercury) lower at one year, and 0.4 mm Hg lower at five years after participating in an intensive weight loss program.
• The percentage of HbA1c, a protein in red blood cells used to test for diabetes, was reduced by 0.26 at both one and five years after participating in an intensive weight loss program.
• The ratio of total cholesterol to good cholesterol ­– known as high-density lipoprotein (HDL) cholesterol – was 1.5 points lower one year and five years after participating in an intensive weight loss program.

Jebb explained that the changes observed in the review are significant as they demonstrate improvements at the population level. In a preliminary finding, it was observed that the reduced risk of developing cardiovascular disease or Type 2 diabetes appeared to persist even after regaining some weight. However, as few studies followed individuals for more than five years, Jebb cautioned that more data is necessary to verify whether this potential benefit endures.

Jebb explained that most trials mainly focus on the effectiveness of new treatments and weight change in the short-term, rather than the effect on later diseases. Additionally, individual studies are often not large enough to detect differences between groups in the incidence of cardiovascular conditions. Since cardiovascular conditions affect only a small proportion of the whole group, studies may not continue long enough to see the effects on “hard” outcomes such as a new diagnosis of Type 2 diabetes or a heart attack.

“Our findings should provide reassurance that weight loss programs are effective in controlling cardiovascular risk factors and very likely to reduce the incidence of cardiovascular disease,” she adds.

According to available evidence, adherence to the American Heart Association’s Life’s Essential 8 health metrics, such as maintaining a healthy weight, eating healthy food, being physically active, not smoking, getting enough sleep, and controlling cholesterol, blood sugar, and blood pressure levels, can improve cardiovascular health.

The review had some limitations, as the information included in it was only updated until 2019 and the review only considered research papers written in English, which may have resulted in some eligible studies in other languages being overlooked.

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