The Impact of HIIT on Appetite Suppression (Leptin Levels) - Foundry Personal Training Gyms

The Impact of HIIT on Appetite Suppression (Leptin Levels)

By now, we all realise that we must Move More to Lose More (balanced diet included), but do you know what is happening at a metabolic level? The hormone leptin is central to understanding these metabolic effects and is critical in regulating hunger and maintaining energy balance. Leptin is produced by fat cells and communicates directly with the brain, specifically the hypothalamus, signalling satiety and helping to regulate energy intake relative to energy expenditure.

However, in overweight situations, leptin signalling often does not function properly, a condition known as leptin resistance, where, despite high hormone levels, the brain fails to receive the correct signals to stop eating.

By influencing leptin dynamics, HIIT may offer an additional mechanism—beyond calorie burning—by which it supports weight loss and health improvements. This exploration aims to provide readers with insights into how integrating HIIT into their routines could enhance their dietary control and overall metabolic health, ultimately leading to more sustainable weight management strategies.


Leptin and Appetite Control

Leptin is a hormone predominantly produced by adipocytes, or fat cells, in the body. It plays a crucial role in regulating energy balance by signalling the brain to inhibit hunger, thereby reducing food intake and stimulating energy expenditure. Leptin is sometimes called the “satiety hormone” or the “starvation hormone” because its levels generally increase and decrease in response to changes in body fat stores. High leptin levels signal the brain that the body has enough fat stored, prompting reduced appetite. In contrast, low levels suggest energy stores are depleted, increasing hunger.

The primary action of leptin is its communication with the hypothalamus, the part of the brain that regulates appetite and energy homeostasis. When leptin binds to its receptors in the hypothalamus, it stimulates pathways that reduce hunger and increase the body’s energy. This hormone is crucial in daily dietary satisfaction and hunger cues, long-term food intake, and body weight regulation. Essentially, leptin helps inform the brain about the current state of the body’s energy stores and influences whether more energy (food) is needed.

In individuals who are overweight or obese, leptin signalling often doesn’t function properly—a phenomenon known as leptin resistance. Despite having higher leptin levels due to more significant body fat, people with leptin resistance do not respond adequately to the hormone. This malfunction means the brain does not recognise the signal to stop eating, leading to increased food intake despite adequate or excessive fat stores. The exact mechanisms behind leptin resistance are not fully understood, but inflammation in the hypothalamus and modifications to leptin receptors have been identified as potential contributors. This resistance can create a vicious cycle where increased body fat leads to higher leptin levels, which should typically lead to reduced appetite. Still, the appetite remains high due to resistance, potentially leading to further weight gain.


High Intensity Interval Training (HIIT)

High Intensity Interval Training (HIIT) involves short bursts of intense exercise alternated with low-intensity recovery periods. Unlike traditional endurance training, which maintains a consistent pace for longer durations, HIIT is characterised by its quick, highly energetic phases followed by brief moments of rest or lower intensity. Depending on the workout plan, this pattern can vary significantly in duration and intensity, but typically, the intense phases last from 30 seconds to several minutes, and the rest periods are equally variable, ensuring the body does not fully recover between intervals.

A typical HIIT session may last 10 to 30 minutes, making it an efficient option for those with limited time. The structure of a HIIT workout generally follows this sequence:

  • Begins with 3-5 minutes of lighter activity to prepare the body and reduce the risk of injury.
  • It consists of 20-90 seconds of intense activity, such as sprinting, jumping, or other aerobic exercises, pushing the body to at least 80% of its maximum heart rate.
  • Follows each high-intensity burst with a period of rest or low-intensity activity lasting roughly the same time, allowing the heart rate to decrease.
  • Ends with several minutes of stretching or less intense movements to help the body transition back to a normal state.

While HIIT is well-known for its efficiency in burning calories and fat in a shorter time frame, its benefits extend far beyond weight loss:

  1. HIIT improves cardiovascular health by strengthening the heart and improving its ability to pump blood efficiently, enhancing overall cardiovascular function.
  2. Post-exercise, HIIT induces a higher rate of metabolism that can last for hours, a phenomenon known as excess post-exercise oxygen consumption (EPOC). This means you continue to burn calories at a higher rate even after your workout is complete.
  3. Unlike steady state cardio, which can lead to muscle loss alongside fat loss, HIIT can help preserve and even build muscle mass due to its incorporation of intense, muscle-engaging movements.
  4. HIIT can help lower blood sugar levels and improve insulin sensitivity, which is beneficial for preventing type 2 diabetes and managing weight.
  5. Regular HIIT workouts can improve overall endurance, enhancing performance in various sports and daily activities.


HIIT and Leptin Levels

Recent scientific research has begun to uncover how High Intensity Interval Training (HIIT) affects physical fitness metabolic rates and hormonal balances, including leptin levels. Studies suggest that HIIT can influence leptin, the hormone responsible for signalling satiety to the brain, thereby playing a crucial role in appetite regulation and energy expenditure. These findings are significant because they link intense, intermittent exercise and potential changes in eating behaviours and weight management.

A study titled “The Impact of High Intensity Intermittent Exercise on Serum Leptin Levels in Sedentary Overweight Adult Women” explored this connection. This research aimed to assess how HIIT specifically affects leptin levels in overweight women at a higher risk of developing leptin resistance.

The study involved 24 sedentary adult women classified as overweight according to body mass index (BMI) criteria. These participants were randomly assigned to two groups: a control group, which did not exercise, and an HIIE group (High Intensity Intermittent Exercise, a form of HIIT), which participated in structured HIIT sessions. The exercise regimen included static cycling at high intensities (80-90% of maximum heart rate) for 60 seconds, alternating with 60 seconds of low-intensity cycling. This pattern was repeated for 20 minutes, preceded by a 3-minute warm-up and a 2-minute cool-down, totalling 25 minutes per session.

The study’s findings were quite revealing:

Both groups had their serum leptin levels measured before the intervention and one hour after the exercise. The results showed a significant reduction in leptin levels in the
HIIE group compared to the control group, indicating that the high-intensity exercise had a measurable impact on this appetite-regulating hormone.

The decrease in leptin levels suggests that HIIT could help reduce leptin resistance in overweight individuals by lowering the leptin levels available to signal the brain, potentially resetting the sensitivity of leptin receptors over time.

These findings support the hypothesis that HIIT may aid in weight loss through calorie expenditure and by modifying hormonal responses that control hunger and satiety. Such hormonal adjustments could help individuals better manage their appetite and thus contribute to more effective long-term weight management.

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Practical Implications of HIIT for Appetite Suppression

The interplay between High Intensity Interval Training (HIIT) and leptin levels offers promising insights into how exercise can control appetite. By engaging in HIIT, individuals may experience a decrease in leptin levels, which, interestingly, could help mitigate the effects of leptin resistance—a common issue in overweight individuals where the brain no longer adequately recognises leptin’s signals to reduce hunger. HIIT could potentially ‘reset’ the leptin sensitivity in the brain, making it more responsive to leptin cues, leading to a natural reduction in appetite and an easier path to weight loss.

The reduction in leptin levels following HIIT sessions can have several beneficial effects on an individual’s dietary habits and overall health:

  • With improved leptin sensitivity, the brain might better perceive signals to stop eating, leading to a natural decrease in appetite. This can help individuals avoid overeating and make adhering to healthier portion sizes easier.
  • Enhanced leptin signalling can help individuals feel satiated with less food, aiding in weight management and reducing the likelihood of binge eating or snacking between meals.
  • Consistent HIIT practice could help maintain lower and more stable leptin levels, contributing to sustained weight loss and preventing future weight gain.

Caveats and Considerations

While the benefits of HIIT in managing appetite through leptin regulation are compelling, there are important caveats and considerations to bear in mind:

  • Individuals’ responses to HIIT can vary significantly. Age, gender, baseline fitness level, and genetic predispositions can affect how one’s body reacts to HIIT and its impact on leptin levels.
  • The effects of HIIT on leptin levels and appetite suppression are not immediate and require consistent practice. Regular engagement in HIIT is necessary to see and maintain these benefits. It’s recommended that people incorporate HIIT into their routine 2-3 times per week, but this can vary based on personal fitness goals and physical condition.
  • As individuals embark on a HIIT regimen, monitoring their body’s responses and adapting their workouts is important. Overtraining or incorrect execution of high-intensity intervals can lead to injury or burnout, which could negate the positive effects on leptin regulation and overall health.


Incorporating HIIT into Your Fitness Routine

Starting a HIIT regimen can be a fantastic way to boost your fitness, but it’s important to approach it carefully to avoid injury and ensure it’s effective. Here are some essential tips for beginners:

  • If you’re new to high-intensity workouts, begin with shorter intervals and lower intensities. Gradually increase the duration and intensity as your fitness improves.
  • Always start with a dynamic warm-up to prepare your muscles and prevent injuries. This could include light jogging, high knees, or leg swings.
  • Before increasing the intensity or speed, perform each exercise correctly. Poor form can lead to injuries and reduce the effectiveness of your workout.
  • Drink plenty of water before, during, and after workouts. Adequate hydration and proper rest are crucial, especially as HIIT can be very demanding on the body.

For a structured and personalised approach, consider joining programs like the Small Group Personal Training at Foundry, where you receive expert coaching in a supportive environment, ensuring your HIIT sessions are effective and safe.

HIIT workouts are versatile and can be done anywhere, with little to no equipment. Here are a couple of examples to get you started:

At-Home HIIT Workout:

  • 30 seconds of burpees
  • 30 seconds of rest
  • 30 seconds of high knees
  • 30 seconds of rest
  • 30 seconds of jump squats
  • 30 seconds of rest
  • 30 seconds of mountain climbers
  • 30 seconds of rest

Repeat for 15-20 minutes.

Gym-Based HIIT Workout:

  • 1 minute on the treadmill at high intensity (sprint)
  • 1 minute of walking (rest)
  • 1 minute of cycling at high intensity
  • 1 minute of slow cycling (rest)
  • 1 minute of rowing at high intensity
  • 1 minute of slow rowing (rest)

Repeat for 20-30 minutes.

Integrating HIIT into your long-term fitness and weight management strategy can significantly enhance your health outcomes. Here’s how you can make HIIT a sustainable practice:

  • Understand your fitness level and set achievable goals. Overly ambitious targets can lead to disappointment or injury.
  • Variety in your workout routine can keep it exciting and challenging. Include different HIIT workouts to engage different muscle groups and avoid boredom.
  • Pay attention to how your body feels during and after workouts. If you feel undue pain or fatigue, give yourself time to recover, and consider adjusting the intensity of your workouts.
  • Keep a workout diary or use fitness apps to monitor your progress and stay motivated. Seeing improvements over time can be a great motivator.
  • Consistency is key in any exercise regimen. Aim to incorporate HIIT workouts into your routine two to three times a week, allowing for recovery days in between.

If you have any questions about the above or would like some advice on how we could help you with your fitness goal, don’t hesitate to visit one of our personal training gyms in London and try one of our small group training sessions. 


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