A research team from the School of Public Health at the LKS Faculty of Medicine, the University of Hong Kong (HKUMed), has found that brisk interval walking performed once a week can significantly improve body fat reduction and cardiorespiratory fitness in adults with central obesity, comparable to exercising three times a week – the traditional recommendation for exercise frequency. The study provides strong scientific evidence supporting the therapeutic use of once-weekly brisk interval walking as a convenient exercise approach for adults with central obesity, particularly for those with time constraints. The findings were published in Nature Communications.
A practical, evidence-based exercise approach to combat excess adiposity
Obesity is a common chronic condition characterised by excessive fat accumulation that impairs health. Excess adiposity, particularly when deposited centrally around the abdomen, is linked to negative health outcomes, including cardiovascular disease, metabolic disorders, and increased mortality risk. While regular exercise provides comprehensive health benefits and is integral to obesity management, sustained physical activity remains insufficient, especially for individuals with obesity.
Interval training involves alternating periods of vigorous exercise with lower-intensity active recovery exercise. It is an effective, time-efficient approach for reducing total body and visceral adiposity compared to traditional continuous moderate-intensity training. However, standard exercise guidelines typically recommend interval training three days per week, which may not be practical for individuals with time constraints and limited access to exercise facilities. While previous studies found that the ‘weekend warrior’ exercise pattern, which condenses weekly exercise into one to two days, to have positive effects, there has been limited scientific evidence on the efficacy of interval training performed in this pattern.
Professor Parco Siu Ming-fai, Professor and Head of Division of Kinesiology at the School of Public Health, HKUMed, emphasised the importance of validating whether once-weekly interval training can be as effective as the traditional thrice-weekly regimen, thus offering a practical, evidence-based alternative.
Less frequent, similar efficacy
Between September 2021 and September 2024, HKUMed researchers conducted a rigorous trial in Hong Kong involving 315 Chinese adults aged 18 or older who were overweight and had central obesity. The participants were randomly assigned to one of three groups: a once-weekly interval training group, a thrice-weekly interval training group or a control group.
The control group attended a 2.5-hour health education session every two weeks over a four-month period. The interval training groups performed a total of 75 minutes of interval training per week, either in a single session or divided into three sessions. The participants’ body fat mass was measured using dual-energy X-ray absorptiometry at three assessment points: before the intervention (baseline), at 16 weeks (post-intervention), and at 32 weeks (four-month post-intervention follow-up).
The trial results revealed that at the 16-week assessment, both the once-weekly and thrice-weekly interval training programmes similarly reduced excess adiposity, as measured by total body fat mass, fat percentage and waist circumference, and improved cardiorespiratory fitness compared to the control group.
‘While thrice-weekly interval training remains a commonly recommended approach for the therapeutic management of excess adiposity, our findings show that once-weekly interval training offers similar benefits and represents a practical exercise strategy,’ said Professor Siu. ‘For many adults with central obesity who struggle to balance work, study, family and other commitments, time constraints are a primary barrier to exercising multiple days per week.’
‘Instead of relying solely on high-frequency exercise prescriptions, once-weekly interval training can be considered a feasible and effective alternative,’ added Professor Siu.
KUMed study finds that, with the same total workout time, weekly brisk interval walking improves fat loss and heart fitness in adults with obesity, comparable to exercising three times a week – the traditional recommendation for exercise frequency.
Professor Parco Siu Ming-fai (centre) said that while thrice-weekly interval training is a commonly recommended approach for treating obesity, the study shows that once-weekly interval training with the same total workout time offers similar benefits and is an effective alternative for busy people.
DH reminds public to take precautions against heat-related illnesses during very hot weather
The Centre for Health Protection (CHP) of the Department of Health (DH) today (July 25) reminded members of the public to take appropriate precautions against heat-related illnesses, such as heat cramps, heat exhaustion and heat stroke, during very hot weather.
In a high-temperature environment, excessive sweating and difficulty in heat dissipation can cause stress to the body. Members of the public should take the following precautions:
- Hydrate in a timely manner to prevent dehydration;
- Wear light-coloured, loose-fitting and breathable clothing to minimise heat absorption and facilitate perspiration and heat dissipation;
- Keep indoor areas well ventilated and maintain appropriate temperature and humidity, e.g. by opening windows or using a fan or air-conditioning;
- Avoid strenuous exercise and prolonged activities such as hiking or trekking;
- Arrange outdoor activities in the morning or the late afternoon, if possible, and bring enough water; and
- Avoid beverages containing caffeine, such as coffee and tea, as well as alcoholic beverages, which may speed up water loss through the urinary system.
In addition, infants and children, the elderly, pregnant women, individuals with chronic illnesses such as heart disease or high blood pressure, overweight people and outdoor/manual workers are more susceptible to heat stroke. These groups should pay special attention to the following:
- Infants and young children: Avoid going outside when the temperature is high. If they must go outside, adults should ensure they stay in places with moderate temperatures and good ventilation or air-conditioning. Infants and young children should never be left unattended in a confined space such as a vehicle;
- The elderly, pregnant women, individuals with chronic illnesses and overweight people: Pay close attention to health conditions and seek help as soon as possible if experiencing any abnormalities in health indicators such as blood pressure, heart rate, etc or if there are fluctuations in health conditions. Avoid going out when the temperature is high. Make sure there is good ventilation, or turn on a fan or air-conditioner to keep an appropriate temperature indoors. High temperatures can also worsen the condition of people with chronic illnesses (such as cardiovascular and respiratory diseases). Therefore, they should have an ample supply of their usual medication and keep in contact with family members, neighbours and the community. People should seek immediate help if they feel unwell.
- Outdoor/manual workers: Reschedule work to cooler hours as far as feasible. If working in a hot environment is unavoidable, provide shade where practicable and use ventilation and heat dissipation equipment. Once work has begun, gradually adjust the pace of work and take breaks in the shade to regain strength.
The DH reminded the public that heat stroke is one of the most common health risks in hot weather. Over the past five years, there have been over 200 hospital admissions due to heat stroke each year in Hong Kong, with two to five fatal cases occurring mainly during the summer months from May to September. Vulnerable groups are more susceptible to heat stroke. Symptoms include dizziness, headache, nausea, shortness of breath or confusion. In severe cases, patients may suffer from convulsions or become unconscious, which can be life-threatening if they are not cooled down and resuscitated in a timely manner.
Members of the public are also advised to pay attention to the latest weather, as well as the real-time and forecasted ultraviolet (UV) index released by the Hong Kong Observatory (HKO). When the UV index is high (6 or above), the public should note the following:
- Avoid direct sunlight exposure to the skin and the eyes;
- Apply broad-spectrum, water-resistant sunscreen liberally, with a sun protection factor (SPF) of at least 30 or higher, when participating in outdoor activities. Reapply every two hours if staying outdoors for long periods, or after swimming, sweating or towelling off;
- While using DEET-containing insect repellents for personal protection against mosquito-borne diseases, apply sunscreen before insect repellent;
- Seek shade;
- Wear UV-blocking sunglasses;
- Wear loose-fitting clothing with long-sleeves; and
- Wear a wide-brimmed hat or use an umbrella.
If symptoms develop, such as dizziness, headache, nausea, shortness of breath or confusion, rest and seek help immediately, and seek medical advice as soon as possible.
For more health information, the public may visit theCHP's heat strokepage andUV radiation page; the HKO's Dial-a-Weather (1878 200),latestweather report and forecast,UV Indexand weather information forhiking and mountaineering; andpress releasesof the Labour Departmenton precautions against heat stroke for outdoor workers and their employers when the Heat Stress at Work Warning is in force.
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