Which diet is the best?

Huge thanks to Naomi Leppitt, RD for her input in this post.

  • There are so many diets out there and a comparison study of Atkins, Slim-Fast, Weight Watchers and Rosemary Conley showed they all result in weight loss of a similar amount (Truby, 2006). 
  • Very low-calorie shake diets (eg Lighter Life, Cambridge, Herbalife etc) result in greater immediate weight loss than standard low-calorie diets and may even induce the remission of diabetes, but over a year, they’re shown to be just as effective as each other (Tsai and Wadden, 2006).
  • What about  low-carb/low-fat diets? Well, in theory- a low carb diet should help with fat loss. When you eat carbs your body releases insulin  part of insulin’s job is to enable cells , to use the energy from carbs or store it. Eating less carbs can mean less insulin = less fat storage. Studies show in the short term, low-carb dieters lose more weight than low-fat dieters, over the longer term, they have similar results (Hession, 2008). 
  • Intermittent fasting diets, like the 5:2 work because on the days you  eat normally, most people will not fully compensate for their fasting days,  they eat less overall; and the fasting period has all sorts of positive effects on how your body processes energy.
  • What about exercise? When comparing dieting alone versus just an exercise regime, a comparison of multiple studies found that more people lose weight with dieting than exercise (Shaw, 2006), and that’s likely because it’s easier to reduce the amount of energy taken in, than try to burn that much more through activity. For example, cutting down a couple of biscuits will save 160kcals but it would take a 30 minute work to expend that amount of energy. However, those that diet and exercise, lose more weight than just dieting alone (Wu, 2009). 
  • So there is not one diet that is necessarily better than another. They can all work IN THE SHORT TERM. This is the key. In fact the research tells us that 80% of weight lost by dieting is regained after 5 yrs.
  • Instead of sticking strictly to one type of diet for the short term, think about what will work for your lifestyle long term. Diets are about changing the balance of your macronutrients and reducing your calories or burning more through movement. So how can you make swaps you can stick to? If you love carbs, do you need to check your portion sizes are not too large? What can you add into your diet to boost the quality? More fruit and veggies can mean less sugary snacks and eating protein at each meal can keep you fuller. Can you build more walking into your day? Quality of life is so important, so any changes need to be sustainable and not make you feel restricted or miserable. 

So how do I achieve healthy weight loss?

When someone wants to lose weight, there is often the desire to lose it quickly. We all want change NOW! However, it’s worth being mindful of the other effects of rapid weight loss and crash diets on your body. When you lose weight fast:

  • That initial fast weight loss is satisfying but it is due to fluid losses. It won’t all be fat.
  • Muscle is lost too as well as fat, which can slow metabolism. This means you use less calories in daily life.  It can be particularly detrimental when you’re older, as it can lead to frailty.
  • By eating minimally you just probably won’t be getting enough nutrients, especially if you are cutting out whole food groups ie no carbs, or no dairy. This can be ok short term but if these changes are for the long term you need to replace those nutrients.

A healthier weight loss approach is:

  1. To make small changes over time that you can keep to for the long term. 
  2. Find a dietary approach that works for your lifestyle and food preferences.
  3. Don’t pick fad diets that cut out whole food groups and promise unrealistic results.
  4. Think about what you can add in rather than what you need to take out. Do you need more fruit and veg, more water, can you have yoghurt as a pudding to prevent that mid afternoon choccie biscuit?
  5. Avoid weigh yourself every day or even each week or even at all… because your body weight is affected by so many things other than what you eat. It can be demoralising and demotivating when the scales don’t change as quickly as you want them to. Think about how your clothes fit and other signs that your weight is changing.
  6. Partner your food changes with some gentle increases in daily activity. You don’t have to sign up to a marathon, but there are some great couch-to-5k programs and at home videos to follow. In fact you can buy my Pilates DVD here.
  7. Be kind to yourself. Allow yourself the foods that you love but eat them in sensible amounts and frequencies.


Hession M et al. Systematic review of randomized controlled trials of low-carbohydrate vs. low-fat/low-calorie diets in the management of obesity and its comorbidities. Obes Rev 2009, 10(1):36-50. doi: 10.1111/j.1467-789X.2008.00518.x.

Truby H, et al, Randomised controlled trial of four commercial weight loss programmes in the UK: initial findings from the BBC “diet trials”. BMJ 2006, 17;332(7555):1418

Tsai AG and Wadden TA The evolution of very-low-calorie diets: an update and meta-analysis. Obesity 2006 14(8):1283-93.

Shaw  KA, et al. Exercise for overweight or obesity. Cochrane Database of Systematic Reviews 2006, Issue 4. DOI: 10.1002/14651858.CD003817.pub3.

Wu T et al Long-term effectiveness of diet-plus-exercise interventions vs. diet-only interventions for weight loss: a meta-analysis. Obes Rev 2009, 10(3):313-23. doi: 10.1111/j.1467-789X.2008.00547.x. 

Hall D.H and K.Scott. Maintenance of lost weight and long term management of obesity. doi: 10.1016/j.mcna.2017.08.012

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