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Nutrition and physical activity are well-known means of weight control and improving cardiometabolic and mental health. At the same time, there are numerous dietary and exercise options, and we all have our own goals within the overarching aim of “being healthy.” Moreover, it’s better the chosen lifestyle to work in the long term. Time-restricted eating (without changes in the food itself) and high-intensity functional training (alternating between intense exercises and recovery) have been recognized as beneficial for weight loss and cardiovascular and brain health. Individually.
Researchers from the University of Sfax in Tunisia investigated how time-restricted eating and high-intensity functional exercises synergize and affect body composition and cardiometabolic health in overweight women.
Time-Restricted Eating and High-Intensity Functional Training Against Obesity
According to the World Health Organization (WHO), since 1990, global obesity rates have more than doubled, and among adolescents, they have quadrupled. In 2022, 43% of adults over the age of 18 were overweight, with 16% of them classified as obese. The primary danger of excess weight lies in its impact on health. It significantly increases the risk of cardiovascular and neurological disorders, type 2 diabetes, cancer, and bone diseases. In 2019, excess weight was responsible for approximately 5 million deaths from non-communicable diseases, including cardiovascular diseases, diabetes, cancer, neurological disorders, chronic respiratory diseases, and digestive disorders.
Insulin resistance alone, a serious risk factor for many dangerous diseases, is a consequence of excess weight. Additionally, it affects the quality of life and reproductive health.
Time-restricted eating (or intermittent fasting) and high-intensity functional training have been recognized as some of the most effective ways to reduce and maintain weight.
Time-Restricted Eating (Intermittent Fasting)
This involves consuming food within certain hours of the day and refraining from eating the rest of the time. Typically, people extend the time between their last evening meal and their first meal the next day. Thus, the calorie consumption window predominantly lasts 6–10 hours per day. Even without changing the diet, such a feeding regimen already offers numerous scientifically proven benefits.
Among them:
- Reduction of fat mass, including visceral fat, while preserving muscles and bones;
- Normalization of lipid metabolism in the body, including cholesterol levels;
- Increased insulin sensitivity and normalization of glucose levels;
- Reduction of inflammation and blood pressure;
- Improvement of mood and sleep.
Extended fasting provides even more benefits, including cellular cleansing and rejuvenation.
High-Intensity Functional Training
One of the most effective workouts for combating obesity is high-intensity interval training (HIIT). However, this type of activity is not suitable for everyone, may be contraindicated for some, and many find it difficult to adhere to due to its monotony. As an alternative, high-intensity functional training has emerged as a new exercise model. According to this model, short periods of intense exercises alternate with periods of rest or active recovery, utilizing multijoint functional movements.
Studies have indicated that such training contributes to the reduction of fat mass, including in people with type 2 diabetes. Moreover, six weeks of activity improve cardiometabolic risk factors and insulin sensitivity.
Therefore, researchers compared how diet and exercise separately affect sedentary women and whether they enhance each other’s effects.
Study Design
Researchers selected 64 women with obesity aged 18 to 45. Participants had a BMI of 31-34 kg/m², waist circumference above 80 cm, and their weight had remained stable for three months before the study. All women were capable of physical activity but had not adhered to a structured exercise program in the previous 6 months. Pregnant women and those breastfeeding within 24 weeks from the start of the trial were excluded from the sample. Additionally, exclusion criteria included cardiovascular diseases, diabetes, medication use, smoking, participation in weight loss treatment, and habitual eating window <12 hours/day.
Participants were divided into three groups, each undergoing a 12-week intervention where they either restricted their eating window, performed high-intensity functional exercises, or did both. The eating window was 16/8, meaning participants only ate from 8:00 to 16:00. Tabata-style functional training sessions were conducted three days a week with an instructor for approximately one hour.
Results
Over the 12 weeks, participants in all three groups experienced significant weight loss and reductions in waist and hip circumference. Plus, all groups demonstrated favorable changes in lipid levels, including cholesterol, and glucose.
Some differences were noted between groups. For instance, fat-free mass (a combination of lean mass and skeletal muscle mass) and blood pressure improved in the “diet + exercise” and “exercise” groups but remained unchanged in the “diet” group.
Overall, participants in the “diet + exercise” group experienced more profound changes in body composition and cardiometabolic parameters than the other groups.
