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Weight Loss – the metabolic challenge to keep going or keep it off!

As the end of the year approaches we try to make Planet Earth a little lighter. Striving for that beach body, aiming to fit into that dress for wedding season or setting a new year’s resolution (again) are popular themes. And often


keeping the weight off is where the challenge lies.

There are a number of reasons as to why this may be the case. What exactly changes as we lose weight? Why is it so difficult to keep weight off? Why do we plateau after an initial weight loss? And why is it that we often end up paying for yo-yo weight loss with a little extra weight gain each time?

Weight loss can be either beneficial or desirable to a wide variety of people. From the overweight diabetic, to the stay-at-home-mom or the endurance athlete certain health or performance outcomes may benefit from carrying less weight, or specifically less fat. These or even simple aesthetic goals are motivating factors that may lead an individual down the path of energy deficit with the aim of shedding pounds. This is achieved by spending more energy exercising, limiting energy intake through food or, ideally, a combination of both.

Aiming to reduce the number on the scale as an only marker of progress often takes priority over anything else with both constructive and destructive consequences. The main benefit of focusing on weight only is the ease of monitoring and the potential motivating factor that lies in seeing that glowing number tick below your goal weight. At the same time, however, this reliance on a scale can also be a limitation to successful weight loss, destroying motivation and also providing a misleading description of body composition. Body composition refers to how much weight is in the form of fat, muscle, water, bone etc. Rapid and acute weight loss is likely to induce a loss of ALL of these tissues and losing functional mass in the form of muscle and bone are not just undesirable but can be detrimental to health. Evidence and strong argument exists for a greater appreciation for strength, function, movement and bone health as predictive measures of various health outcomes.

Weight loss through significant energy restriction results in a number of changes that occur within our bodies at a cellular level. An energy deficit (more out than in) brings about adaptive responses as the body looks to conserve energy in what could be described as a survival mechanism. The body limits losses of energy through reducing energy expenditure, improving the efficiency and economy of the systems that use fat or carbohydrate to produce energy and increasing the desire to eat. These changes make both the success of, and adherence to, any lifestyle modifications more difficult to achieve.

The total amount of daily energy that we expend (TDEE) is made up of 4 components.

  1. Our resting metabolic rate makes up most of the TDEE in non-elite endurance athletes. This is the energy required to keep us alive and functioning at rest, sitting in a chair or lying down with little stimulation.
  2. Non-exercise activity thermogenesis is the energy required to move, fidget, make a cup of coffee or menial tasks.
  3. Exercise activity thermogenesis is the energy required for structured exercise, a jog, the gym or a few laps of the pool.
  4. The thermic effect of food is the energy required to digest, absorb and use the food we eat after a meal.

Each of these components are blunted (relatively speaking) as a result of rapid weight loss meaning we spend less energy doing our normal day to day tasks.

  • Our basal metabolic rate slows as we lose muscle mass and other active tissue including bone. Hormonal changes further reduce this too.
  • Non-exercise thermogenesis is reduced as we consciously or unconsciously tend to move a little less, an effect that also seems to persist beyond the period of weight loss.
  • There is a minor reduction in the thermic effect of food, mainly because we are eating less.
  • The energy spent during exercise is also relatively less because less weight is carried during exercise and also because the body improves it’s economy of exercise (greater output for less energy). Granted we often exercise more so total volume increases here.

Within our cells, the little guys called mitochondria who are responsible for producing energy are getting better at their job in this state, using less fat or carbohydrate from what we eat or have stored to keep us functioning, moving and exercising.

There are also hormonal changes that occur during calorie restriction that play a role in these adaptations as well as affecting our hunger cues. Production of thyroid hormones change which slows metabolic rate further. Leptin, the hormone released by fat cells responsible for telling us when we are full, is reduced due to low energy intake and the reduced levels of body fat. Insulin, another stimulator of satiety and regulator of metabolism, is also reduced. Testosterone levels are lower which reduces muscle synthesis, muscle being a strong promoter of metabolic rate. Testosterone also limits fat synthesis, thus a low level does not assist keeping fat production in check with weight regain. Ghrelin, an appetite stimulant, increases in response to low energy intake to keep us hungry. And finally cortisol production also increases breaking down muscle (lowering metabolic rate) and working against leptin to keep us hungry too. Many of these hormonal changes persist even after the calorie deficit is removed, a likely contributing factor to weight regain.

All in all it seems like the cards are stacked against us when trying to lose weight, but some practical application can improve the outcome.

  1. Diet on as many calories as possible

    A fantastic term I heard recently (although I cannot credit the source as memory fails). Essentially the most food you can eat to lose weight at a good rate (500-1500 g per week). This narrows the energy deficit and limits the survival responses described above.
  2. Use a step-wise energy deficit

    This means constantly adjusting your calorie intake as you lose weight. Don’t shock your body into starvation, start with a small reduction (see point 1) and narrow energy deficit and go from there.
  3. Refeeding

    This is a fantastic tool in the weight-loss toolbox (and a topic for a post on its own!). Refeeding is not a cheat day but specifically uses increasing calories, mainly from carbs, for a day to bump up metabolic rate and increase leptin production. Using this with clients I have found it is often a nice psychological booster and allows for some flexibility with your diet too. I will write a more detailed piece on this soon.
  4. Reverse dieting

    Another topic that I will give more time to in due course. This is the nutrition plan that needs to be implemented once your goal weight is achieved to accommodate the lingering effects described earlier. Returning to a “normal” dietary intake immediately runs the risk of weight regain and metabolic disturbances. This is particularly important in very low carb or ketogenic diets that have become popular. In essence it would be a stepwise increase in calories (opposite to point 2) with a focus on how much and when you are eating your macronutrients (carbs/fat/protein).

Set yourself realistic, little goals. If there is information that struck a chord with you in this article see if any of the adjustments suggested help in getting you going again.

If you need more advice or a specific nutrition plan find a dietician in your area ( If you are interested in a metabolic assessment to measure your metabolic rate and how your body functions in using fat and carbohydrate get in touch. We are launching new services to clients and patients in Cape Town based on these principles.

Keep active. Eat food. Not too much. Mostly plants.

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2 Responses to Weight Loss – the metabolic challenge to keep going or keep it off!

  1. Tess Nov 24, 2014 at 3:26 pm #

    great post, particularly like the “diet on as many calories as possible” – I’ve heard this before and believe it’s so important

    • Food For Sport Nov 24, 2014 at 4:51 pm #

      Thanks Tess. It sure is a great way to approach weight loss. Simple and effective starting point!