8 factors that affect rate of weight loss

Emma White - Nutritionist

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When people start a weight loss diet, understandably they'd like to know how long they might be on their journey for. There are ways to estimate how long it may take to lose a certain amount of weight, but as our bodies are unique, everyone's journey will be different.

Factors that can affect speed of weight lossinclude age, gender, diet history and dietary approach – to name a few.

To help you know what is 'normal' when it comes to a healthy rate of weight loss, I've highlighted some important factors below.

The science

As we know, weight loss comes down to creating a calorie deficit. How much you lose in a week will depend, in part, on how big a calorie deficit you've created. It's generally accepted that 1lb of fat contains 3,500 calories, so to lose a pound of fat you need to create a deficit of 3,500 calories. This equates to 500 calories per day over seven days (one week). So, on this basis, if you are aiming for 2lbs loss per week, you'd need to create a 7,000 calorie deficit – or 1,000 calories per day. This is the calculation we use to set your Nutracheck calorie target, to achieve weight loss at the weekly rate you select.

This is a theoretical calculation which is a very useful guide to estimate rate of weight loss, but again – everyone is individual, and this calculation also depends on your starting weight. Working out how many calories someone needs to maintain their weight can only be an estimation when using formulas, so when the calorie deficit is applied, we need to keep in mind that the predicted rate of weight loss is only a guide. As we lose weight, our energy requirements also reduce, so the deficit we're creating won't be as large over time, unless we regularly adjust our calorie target. A good initial rate is 2lbs per week, but it is quite normal that this may slow down the closer you get to your goal.

Recommended safe rate

General guidance is that a 1-2lbs (0.5-1kg) weight loss per week is a good rate for long-term, sustainable results. It's common to experience larger losses early on due to a loss of water in the body, but ideally your weekly rate should be around this suggested amount. If you reach a time in your journey when you feel things should be going faster, it is a useful check to work out your average weight loss per week over the time you have been on your journey (take your total weight lost and divide by how many weeks you have been going). More often than not, you will find it is right on track with the 1-2lbs ideal rate!

Of course it's possible to lose weight faster than 2lbs per week, but it requires a drastic reduction in calorie intake. For most people, creating a calorie deficit large enough to achieve this on an ongoing basis, would be very diffcult to maintain. In the long run, this is incredibly hard to stick to and may potentially lead to nutritional deficiencies.

Rapid weight loss

A question often asked is 'does losing weight faster than 2lbs per week mean there is a bigger risk of gaining the weight back?' There is research to show that regardless of whether a certain amount of weight is lost over a few weeks or several weeks, in the long term, weight regain is the same regardless [1]. But what we do observe in the cases where weight loss is fast is that more fat-free mass – essentially muscle mass – tends to be lost, and this does have an impact on weight regain [1].

Muscle mass plays a crucial role in a healthy metabolism, as muscle burns more calories at rest than fat – so the more lean muscle we have, the more calories we use each day. Losing muscle mass during rapid weight loss can have a lasting effect on our metabolic rate, making weight loss and weight maintenance harder in the long term.

Losing weight gradually, by making a modest calorie reduction you can stick to, is a far better long-term solution than going on a crash diet. The 'lose it quick' mentality can lead to unhealthy eating behaviours, and really doesn't teach anything about how to create a healthy lifestyle longer term. The ideal is to make diet and lifestyle changes you can stick with, and these will then become healthier habits that you do without thinking – rather than viewing a 'diet' as a temporary solution and going back to old habits once you've hit your goal.

Factors affecting rate of weight loss

Factors affecting rate of weight loss

Even if we follow the exact same diet and calorie intake – our rate of weight loss is governed by other factors. Some of these we have no control over, but there are others we do. And we can make some positive impact.

  1. Age – when we're younger we tend to have more muscle mass. As we age, we start to lose lean muscle (which is why I often talk about resistance or weight training being really important as we get older). This loss of muscle has an impact on our metabolic rate. In weight loss terms, it means someone in their 20s or 30s is likely to lose weight a little faster than someone in their 40s, 50s or 60s.
  2. Weight – generally speaking, the more weight we have, to lose, the faster the weight will come off initially. Although this may initially be more water loss than fat, it's a great motivator at the start of your journey!
  3. Sex – biologically, males tend to have more muscle mass than women, and females tend to store more fat. This is all thanks to our hormones! It means that males lose weight at a faster rate than females, certainly initially, as their metabolic rate is higher.
  4. Genes – our genetics play a big part in how we store or mobilise fat, and some people are more predisposed to gain weight more easily. If you feel this is you, I'd encourage you by saying it doesn't mean you can't lose weight, but it's helpful to have realistic expectations...you will get there, but your journey may be a little longer.
  5. Activity levels – the more active we are, the more calories we'll burn day to day. It's also likely we'll maintain more muscle mass through being active, which also helps to maintain a healthier metabolism. All in all, this means people who are more active tend to lose weight more consistently than those who don't do much activity.
  6. Body composition – as has been mentioned a few times now, muscle mass helps us to burn more calories, so the more we have, the faster our metabolic rate will be.
  7. Lifestyle – stress and lack of sleep can have a huge impact on our rate of weight loss. Both can lead to an increase in the hormone cortisol, which can stimulate our body to store more fat, especially around the belly.
  8. Dieting history – someone who has never been in a calorie deficit before, is likely to find weight loss happens a little easier initially, than someone who has yo-yo dieted for a number of years. This is because losing weight and regaining weight, or spending a significant length of time in a calorie deficit causes changes within our body which can affect appetite control, hormones and even motivation. For more on this, check out my blog all about weight loss plateaus.

Summary

Weight loss is not an exact science, it's important to remember that your journey may not look like a perfect downwards-sloping graph. Most people experience blips and sometimes pauses, but if you maintain a moderate calorie deficit and keep going, your weight loss trajectory will be downwards. Eat well for your body, and move as much as you can. Don't compare yourself to others, everyone's journey is different. Focus on your success and progress. Be consistent and you can expect long-term success.

Nutritionist Emma White (ANutr), MSc Human Nutrition is passionate about how food science applies to the human body, and how the nutrients in what we eat affect us and ultimately have an impact on our health.

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