Obesity is a significant global health concern, acting as a major risk factor for cardiovascular and metabolic disorders, and increasing the risk of all-cause mortality. Lifestyle modifications, including physical activity, are a cornerstone of obesity treatment, leading to better outcomes than pharmacological interventions. While restriction of energy intake is effective for weight loss, exercise excels in reducing visceral adiposity and maintaining lean body mass, while also increasing cardiorespiratory fitness (CRF). This article explores the benefits of different interval weight loss approaches, including High-Intensity Interval Training (HIIT) and Intermittent Restricted Eating (IRE).
High-Intensity Interval Training (HIIT) vs. Moderate-Intensity Continuous Training (MICT)
The Challenge of Traditional Exercise Recommendations
Current obesity treatment guidelines often suggest moderate-intensity continuous training (MICT). However, patient compliance with these recommendations remains low, primarily due to the time commitment required to achieve clinically significant weight loss (≥5%) without dietary restriction. Guidelines suggest at least 225-420 min of MICT to obtain clinically significant weight loss without dietary restriction. The lack of time is a common reason limiting exercise.
HIIT as a Time-Efficient Alternative
High-intensity interval training (HIIT) has emerged as a popular strategy in weight loss programs due to its time-sparing nature. HIIT involves short bursts of high-intensity exercise alternating with periods of low-intensity exercise. This allows individuals to accomplish equicaloric training sessions in significantly less time (up to 40% less time) and seems to be at least non-inferior to MICT in terms of changes in body weight and even superior in reducing body fat. Moreover, HIIT induces greater improvements in CRF and cardiometabolic disorders.
Comparing HIIT and MICT: A Study on Obese Adults
A study was conducted to evaluate whether a 12-week HIIT program was non-inferior to MICT in terms of weight loss in healthy obese adults. The study randomized 44 obese subjects to either MICT (60% of maximal oxygen peak, VO2peak) or HIIT (3-7 repetitions of 3 min at 100% of VO2peak interspersed by 1.5 min at 50% of VO2peak) for 12 weeks. Both groups underwent a nutritional evaluation and were given a tailored hypocaloric diet.
Key Findings
The results showed that MICT and HIIT had comparable effects within groups in weight loss (−6.0 kg vs −5.7 kg), changes in fat mass (−2.9% vs −3.6%), fat-free mass (−5.3% vs −5.5%), diastolic blood pressure (−5.5 mm Hg vs −5.8 mm Hg), and low-density lipoprotein cholesterol (−16.4 mg/dL vs −14.7 mg/dL). However, there was a significant difference between groups in VO2peak (HIIT: +461.6 mL; MICT: +170.5 mL; p<0.001) and duration of sessions (HIIT: 35.0 min; MICT: 46.5 min; p<0.001).
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Implications
The study suggests that HIIT, a time-sparing exercise mode, could be at least as effective as MICT for weight loss in obese adults. HIIT allows to accomplish equicaloric training sessions in a significantly shorter period.
Intermittent Restricted Eating (IRE)
The Concept of Intermittent Restricted Eating
Intermittent restricted eating (IRE) is a weight loss approach that advocates alternating periods of weight loss and weight maintenance. The theory behind intermittent restricted eating focuses on avoiding the metabolic, endocrinologic, and behavioural adaptations that occur with sustained energy reduction.
Interval Weight Loss (IWL) Program
The Interval Weight Loss (IWL) program is a commercial online weight loss program based on the principle of intermittent restricted eating (IRE). The program advocates alternating a one-month period of weight loss with a one-month period of weight maintenance. In addition, the program advocates good exercise and sleep habits.
Principles of the IWL Program
The IWL program has six core principles:
- You can’t fight evolution: Impose weight loss breaks every second month to allow your body to adjust to its new set point.
- Overcoming food addiction: Reach for nature first: Retrain your brain and swap processed goods for nature’s treats.
- Nutrition: The full rainbow: Eat more vegetables than you are used to and fill your plate with vegetables first.
- Portion control: Use chopsticks: Eat big to small throughout the day and use a teaspoon, oyster fork or chopsticks with your evening meal to slow down the pace of eating.
- Exercise: Choose to move: Incorporate incidental activity into your daily routine and focus on variety during weight loss months.
- Better sleep: No blue light after twilight: Switch off all technology for two hours before bed and focus on hobbies such as reading, or tackle your to-do list.
Effectiveness of the IWL Program: A Real-World Study
A study reported on the effectiveness of the IWL online platform in a real-world setting. The results focused on 1705 users who subscribed to the program past a 30-day free trial period.
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Key Findings
The study found that weight loss from the first to final recorded measurement and the predicted weight loss from the mixed model at 12 months were statistically significant, averaging 1.2 kg. In terms of clinical impact, 62% of subscribers in the program past 365 days lost ≥5% of their body weight, a target consistently associated with improvement in health outcomes.
IRE and Resting Energy Expenditure (REE)
Sustained or continuous energy restriction results in a reduction in resting energy expenditure (REE). The reductions seen in REE are greater than what would be expected based on body composition changes, and this “adaptive thermogenesis” is thought to be a major cause of weight recidivism in long-term energy deficit. IRE may help mitigate this decline in REE.
IRE vs. Continuous Energy Restriction
A recent systematic review comparing IRE to continuous energy restriction showed a statistical but not clinically significant difference in weight and fat mass in favour of IF and significant improvements in insulin resistance in the IF trials. Another systematic review and meta-analysis investigated the effectiveness of intermittent restricted eating (IRE) when compared with continuous energy restriction in reducing the decline in REE. There was a significant difference in the decline in REE between the intermittent and continuous groups, in favour of the intermittent group (less reduction); there was no significant between-group difference in weight change or BMI.
Intermittent Fasting (IF)
Different Approaches to Intermittent Fasting
Intermittent fasting (IF) is an eating plan that switches between fasting and eating on a regular schedule. There are several different ways to do intermittent fasting, but they are all based on choosing regular time periods to eat and fast. For instance, you might try eating only during an eight-hour period each day and fast for the remainder. Or you might choose to eat only one meal a day two days a week.
Potential Benefits of Intermittent Fasting
Research shows that intermittent fasting is a way to manage your weight and prevent - or even reverse - some forms of disease. Mattson's research shows that it can take two to four weeks before the body becomes accustomed to intermittent fasting. You might feel hungry or cranky while you're getting used to the new routine.
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Intermittent Fasting and Health
Research shows that the intermittent fasting periods do more than burn fat. One of Mattson’s studies published in the New England Journal of Medicine revealed data about a range of health benefits associated with the practice:
- Thinking and memory.
- Heart health.
- Physical performance. Young men who fasted for 16 hours showed fat loss while maintaining muscle mass.
- Type 2 diabetes and obesity. In animal studies, intermittent fasting prevented obesity. And, in six brief studies, obese adult humans lost weight through intermittent fasting. People with type 2 diabetes may benefit: Most of the available research shows that intermittent fasting can help people lose body weight and lower their levels of fasting glucose, fasting insulin and leptin while reducing insulin resistance, decreasing levels of leptin and increasing levels of adiponectin.
- Tissue health.
Considerations Before Starting Intermittent Fasting
It’s important to check with your doctor before starting intermittent fasting. People with type 1 diabetes who take insulin. While an increasing number of clinical trials have shown that intermittent fasting is safe in people with type 2 diabetes, there have been no studies in people with type I diabetes. Keep in mind that intermittent fasting may have different effects on different people.
The 16:8 Intermittent Fasting Plan
The 16:8 intermittent fasting plan is a form of time-restricted fasting that may help with weight loss. It involves not eating for 16 hours and consuming all calories over the remaining 8 hours. The 16:8 eating schedule may help people lose weight and prevent type 2 diabetes and other obesity-associated conditions.
Benefits of the 16:8 Plan
Research on intermittent fasting, including 16:8 fasting, indicates that it may provide the following benefits:
- Weight loss and fat loss: Eating during a set period can help people reduce the number of calories they consume and may also help boost metabolism.
- Disease risk reduction: Supporters of intermittent fasting suggest that it can reduce the risk of several conditions and diseases, such as type 2 diabetes, heart conditions, and rheumatoid arthritis.
- Extended life span: Intermittent fasting, such as 16:8 fasting, may help increase life span and promote a higher quality of life.
Risks and Side Effects of the 16:8 Plan
The 16:8 intermittent fasting plan has some associated risks and side effects. As a result, the plan is not right for everyone. Potential side effects and risks may include:
- Feeling unwell and experiencing headaches, lethargy, crankiness, and constipation
- Excessive weight loss in older adults
- Overeating or eating unhealthy foods during the 8-hour eating window due to excessive hunger
- Harm to people living with certain health conditions or taking certain medications.
People with a history of disordered eating may wish to avoid intermittent fasting. The National Eating Disorders Association warns that fasting is a risk factor for eating disorders. The 16:8 intermittent fasting plan is unsuitable for those who are pregnant, breastfeeding, or trying to conceive.
Tips for Following the 16:8 Plan
People may find it easier to stick to the 16:8 intermittent fasting plan when they try:
- Consuming water regularly throughout the day
- Infusing water with lemon, lime, or cucumber to make it easier to drink
- Watching less television to reduce exposure to images of food, which may stimulate a sense of hunger
- Performing aerobic exercise, which may help suppress appetite in some individuals
- Practicing mindful or intuitive eating when consuming meals
- Trying meditation during the fasting period to allow hunger pangs to pass
Interval Training and Speed Training
Interval Training for Cardiopulmonary Rehabilitation
Physical training is beneficial and should be included in the comprehensive management of all patients with COPD independently of disease severity. Different rehabilitative strategies and training modalities have been proposed to optimize exercise tolerance.
Speed Training as a Form of HIIT
Speed training is also referred to a form of high-intensity interval training (HIIT) or sprint interval training (SIT), which plays a key role in eliciting fat loss. As we look at ways to burn body fat we first have to consider that speed training is only a component to a well-structured approach to weight loss.
Designing a Speed Training Program
When designing a speed training program the basic guidelines supported by many studies tell us that a program can be structured based on a variety of ways to manipulate work to rest ratios. When designing a speed training program, duration, frequency and intensity should be the primary variables to consider. Both a short and a long program should always begin with a 5-10 minute warm-up and conclude with a 5-10 minute cool down.