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Is Running for Weight Loss a Good Idea?

Updated: Mar 7, 2023

Onetrack speaks to Dietician & Professional Runner, Maddie Alm, to bust some myths around running for weight loss.

When trying to combine running and losing weight, how should someone approach their eating habits?

Losing weight while training can be a delicate approach. There does need to be a small calorie deficit, but if there’s too much of a deficit, your metabolism slows down working against your goals. To support weight loss goals without depriving your body of the nutrients it needs, focus on eating more consistently throughout the day. Try not to go more than 3-4 hours without eating. Incorporate plenty of lean protein at meals and snacks to support the growth of lean muscle mass and to help you feel full and satisfied for longer.

What is a calorie deficit and what is it not?

A safe and sustainable weight loss goal is about 0.5-1 pound per week, and one pound is equivalent to 3500 calories, so a deficit should only be about 250-500 calories per day. Many people think eating as little as possible will get them the best and quickest results, but in doing so they often end up eating 1200 calories a day or less, which are the calorie needs of a 2 year old! If you take that approach, you will likely see weight loss initially, which is typically the result of a decrease in muscle mass and a loss of water weight. After a couple of weeks however, the weight loss will slow down and plateau due to a decrease in metabolic rate and ultimately become a frustrating battle. Even though a slow weight loss journey takes time and patience, the bottom line is that you will be able to sustain it and continue to see results.

Are there risks of trying to lose weight and run simultaneously?

If you decrease calories, especially from carbs, and increase aerobic exercise too quickly, you can increase your risk of ending up in a state of low energy availability. This can cause a decrease in energy, fatigue, micronutrient deficiencies, and can increase your risk of becoming injured. All of these side effects of under-fueling are things that can interrupt your training, and since consistency is key when it comes to weight loss, they won’t help you achieve your goals.

Is it all about macros?

Yes and no. A big part of getting adequate calories means also getting these calories from the right foods. With weight loss, prioritizing protein over carbs and fat can help build lean muscle mass, boost metabolism, and reduce cravings. However, ignoring carbs and fat can work against weight loss in their own ways. With that said, it’s all about balance. You want to make sure your meals contain a balance of carbs, protein, fruits/veggies, and healthy fats.

Does your metabolism get “used to running” and so do you have to shake it up?

When you first start training, you can see a more dramatic increase in metabolism. However, as you continue to train consistently, this increase becomes less and less extreme. This is typically when people see their weight loss progress begin to slow down or plateau. This is normal! Keep in mind that with training will come an increase in muscle mass, which can cause the number on the scale to appear the same or higher than it was but isn’t the same thing as weight gain. Muscle is the most metabolically active tissue, so the more muscle mass you can add the greater effect it will have on your metabolism and thus fat loss.

If a pro athlete wants to lose some weight, how do they go about it?

Most athletes think in terms of weight loss, but I encourage athletes to think in terms of body composition changes. A pound of muscle and a pound of fat both look the same on the scale, but do vastly different things for performance. If you lose a pound of fat and gain a pound of muscle, that’s a favorable change for performance but if you just focus on the number on the scale, you may feel discouraged. If you lose a pound of muscle you may think you’ve succeeded in weight loss but you’ve actually lost some of your training adaptation, which will not help you achieve your goals. That said, most athletes I work with see their body composition fluctuate throughout the season without changing anything about their fueling. When you go from a base mileage phase to a higher intensity phase, if you’re fueling properly you will naturally see an increase in muscle mass. None of this can happen if you’re under fueling. So, my advice is to focus on fueling properly to support your training day to day and you will see body changes occur naturally in response to training throughout the year.

How do we know when we are at the right weight for us?

This is a really hard metric to gauge. Weight can change quite a bit from day to day, as well as throughout the day. It’s normal for weight to fluctuate 5-10lb throughout the course of one day! Our weight is made up of muscle and fat mass, but it’s also determined by organ size, how much you’ve eaten, waste/excrement in blood and GI tract, hydration status, water retention, menstrual cycle phase for females, hormones, and more. The “right” weight for you can change depending on what you’re doing with training, as well as age, gender, etc. Instead of focusing on the number on the scale, focus on how you’re feeling. Do you have energy to get through workouts and through the day? Are you sleeping well? Are you sore all the time? If you’re doing well in training and feeling energised, then your fueling and likely your weight are in the right place. If you’re feeling sluggish, sore, or just generally fatigued you likely aren’t fueling properly to perform your best so even if your weight is lower, your performance will suffer.

How much can performance suffer without appropriate fuelling?

RED-S, or Relative Energy Deficiency in Sport, is a major downside to underfueling. This is a condition in which your body doesn’t have the fuel it needs to support your training, let alone day to day functions, and several different systems of your body take a hit. This can include:

  • GI system - impaired digestion and absorption, increased risk for GI issues

  • Immune system - becomes suppressed, increased risk of illness

  • Musculoskeletal system - increased risk for injuries, especially bone related injuries, and poor recovery

  • Hematological - poor blood health, such as low iron or deficiencies of other nutrients

  • Metabolic system - decreased metabolism, resulting in increased fat mass

  • Endocrine system - hormone imbalances, this can lead to loss of menstrual cycle in female athletes

  • Cardiovascular system - decreased endurance capacity

As you can see, none of these symptoms will help improve your performance. Even if you weigh less, which is what most athletes think will improve performance, that will be canceled out by the negative impact underfueling has on all of these other systems of your body.

Is there such a thing as a set point? What is a set point?

The idea of a “weight set point” is based on a theory that your body has a certain weight range in which it will always stay regardless of diet and exercise. While this is a complicated theory, there is a degree of truth to it. Even if every single person on the planet ate and trained the exact same, we would all still look very different from one another. That said, there is a lot of societal pressure to look a certain way in order to be considered an athlete. This often leads to individuals trying to shrink their body, typically in an unhealthy way. As mentioned above, it’s much more useful to focus on performance measures, ensure adequate fueling, and to find an individualized and sustainable approach than it is to try to look like someone else. I always tell athletes that if they start eating what their body needs and they gain weight, they most likely weren’t at a healthy weight for their body before.

Carbs vs Keto for weight loss whilst on a running programme.

Cutting our carbs with endurance training is not the answer for weight loss, especially for female athletes. Your body needs adequate fuel in order to build and maintain lean muscle mass, and on top of that to support training efforts. If you don’t eat carbs, your body’s main source of fuel for exercise, your body has to find that fuel somewhere. Most people assume you just burn up fat, but you actually end up breaking down muscle tissue. Decreasing lean muscle mass combined with inadequate fuel actually slows down your metabolism and increases fat mass, making it much harder to achieve your goals. Instead, focus on building balanced meals and snacks that include quality sources of carbohydrates and eating consistently throughout the day. This will not only allow you to achieve your goals, but will be something you can maintain for the rest of your life. Consistency and sustainability are key when it comes to weight loss, so extreme approaches such as cutting out all carbs typically don’t work or last long and are followed by a period of extremely unhealthy eating.

For more information about fuelling for performance, visit

To find out more about Onetrack creating a bespoke nutrition plan to boost your performance, please email Prices start from £120 per month.

Onetrack empowers everyday athletes with elite training knowledge. Our goal is to bridge the gap between elite sport and everybody in the pursuit of performance. We do this by providing access to physiological testing and intrinsic biomechanical assessments and personal training in our studio spaces in Farnham & Soho as well as offering online run coaching to those further afield. Onetrack Run Club is our community offering; a support crew to motivate you and an expert coach to guide you.

Onetrack was founded in 2016 and has grown organically from the sponsorship of two athletes to become a virtual and physical community that has supported thousands of runners through our studio services, run clubs and running app. Onetrack has been featured by Sunday Times Style, Evening Standard, Independent, Metro, Women’s Health, Selfridges, Runner’s World & more.

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