If you have ever tried to lose weight, chances are at some point you have followed a strict diet plan. The this-will-fix-everything diet. The kind of diet you need to eat everything in sight the weekend before you start it. You mean business.

This diet has it all, and she will fix it all. She’s four lettuce leaves and a chicken breast three times a day. There’s no chocolate, alcohol or joy. Because that’s what gets results. Right? *crickets*. True, she will get you results. But she might not even be necessary.

What Makes a Diet Successful?

A successful diet will get you the results you want, be that muscle gain, fat loss or athletic performance. Success is subjective and person-specific. If the aim of the diet is weight loss, we need to make dietary decisions that create a calorie deficit [1].

Regardless of your food choices or timing, if you do not achieve a calorie deficit, you will not lose weight.

Therefore, in order for a diet to be successful, the individual must adhere to it. This is particularly relevant in weight loss diets. Throughout literature, dietary adherence is consistently associated with successful weight loss[2].

Adherence requires effort, no matter how “good” your diet plan is.

What Makes a Diet Strict?

A strict diet is obviously unique to the individual. However, there are some common characteristics of a “strict” or rigid diet. Strict diets tend to err on the side of dichotomy – you’re either “on” or “off” plan. There are “forbidden” foods that the dieter cannot touch (read: anything sugary, fried or remotely delicious). Consuming “off plan” foods typically leads the dieter to overeat, binge or lose motivation to maintain habits [3].

These are typically “meal plans” sold by your favourite influencer, or the diet where you subsist solely on kale and human tears. Refer to Yolanda Hadid’s speech on almonds for context. A strict diet typically requires more cognitive restraint (effort) to follow than a more flexible dietary approach [4].

Whilst the #cleaneating grind may get you a few Instagram followers, long-term is it any more successful than including bread in your diet?

What Makes a Diet Flexible?

So, you don’t want to hate yourself to your goals. Nice.

Flexible dieting is the antithesis to a rigid diet in literature. A flexible diet is typically less “strict”, and requires less cognitive restraint. Flexible diets are associated with less disinhibition (read: you say fuck this I’m out à lá Gemma Collins), less binges and better weight maintenance long-term[5].

As with strict dieting, flexible is unique to the individual.

So, Everyone Should Just Follow IIFYM, Right?

This is where we take a little pause before we confuse macro counting with flexible dieting. If It Fits Your Macros (IIFYM) or macro-counting is a dieting strategy whereby dieters can eat whatever foods they wish, provided they reach their specific carbohydrate, fat and protein targets.

Whilst this is technically more flexible than a meal plan as it allows for more food variety, I would be cautious against labelling this as “flexible”, in particular in the bodybuilding community.

If dieters are required to hit specific numbers to the gram, that seems pretty rigid to me. But that’s a debate for another time.

Science vs Broscience: Enter Google Scholar

Armed with our definitions of what makes a diet strict or flexible, we now turn to our old friend Google Scholar to pit Clean Eating vs Team Actually Eating Bread and determine who gets results, and why.

Who Gets Results?

We know by now that any diet that places the individual into a calorie deficit will elicit weight loss. Both flexible and rigid diets are successful in generating weight loss, across all populations. From the overweight [4] to seasoned weight trainers [6], literature has shown success between both approaches in reducing body fat when a calorie deficit is achieved.

Who Keeps Results?

So, flexible and rigid diets both achieve weight loss. But herein lies the key question – which approach is better for keeping the weight off?

*enter the Joan Calamezzo Gotcha dancers*.

Maintaining results of a diet is notoriously difficult, particularly in the acute phase of achieving a target [7]. I’m sure anyone who has ever dieted for a holiday, wedding or major life event can attest to this. You hit a target, you get the Instagram… and then what? To maintain weight loss, the individual must maintain an isocaloric diet (eat to maintenance calories).

My God, what an idea. Why didn’t I think of that?

There is no diet that is associated with optimal maintenance of weight loss. Rather, the individual must maintain the habits that got them to where they are[8].

Now, this is where we see the cracks in the pillars of the strict diet.

The Long-Term Problems With Strict Diets

Rigid diets are associated with more emotional and binge-eating episodes, and a greater degree of impulsive behaviour[5]. This is not ideal if overall health is your goal. Impulsive “screw-it” moments can completely derail your progress, and chip away at you. These feelings of failure and shame are not conducive to health.

Strict diets are associated with increased food cravings[9]. Makes sense. You always want what you can’t have, be it chocolate or emotionally available men. Similarly, when you can’t have something, as humans we tend to focus on this. Cravings make us more prone to binges and blowouts, which can derail our maintenance.

Strict diets are associated with increased food and body focuses[3]. Food preoccupation is a big old yikes in literature, and is associated with binge-eating and feelings of deprivation[10]. Rigid dieters tend to be overly concerned with their size and report more mood disturbances[11].

Not a vibe.

More troublingly, the problems associated with rigid diets are also characteristics of many eating disorders. A focus on attaining a thin physique, perfectionism, emotional volatility, cognitive inflexibility are all risk factors for developing eating disorders [12].

Of course, that does not mean to say that anyone who eats chicken and broccoli has an eating disorder. However, it is something to consider when setting up your dietary strategy for the long-term.

Conclusion

Thanks to Instagram, hopefully you now know that it’s all about that calorie deficit bro.  Achieving the calorie deficit can be troublesome, and is worth giving serious thought to.

Before you decide to embark on a five-eggs-per-bloke-per-day diet, it may be worth asking yourself can I see myself sticking to this for the rest of my life? In most cases the answer is no. And what happens if you can’t stick to it?

How can you best set yourself up for long-term success? Is kale salads with your tears as a garnish realistically what you see yourself doing for the rest of your life?

As always, I’m super curious to hear your thoughts. Unless you disagree with me, then please keep scrolling. This is an echo chamber, not a discussion forum – xoxo

References

1. Jennings, J.H., Lesser, M. (2012) ‘Weight loss and calorie restriction at 50% fasting rate’, Pakistan Journal of Nutrition, 11(3), pp. 282-287.
2. Alhassan, S., Kim, S., Bersamin, A., King, A.C., Gardner, C.D. (2008) ‘Dietary adherence and weight loss success among overweight women: results from the A to Z weight loss study’, International Journal of Obesity, 32, pp. 985-991.
3. Westenhoefer, J., Engel, D., Holst, C., Lorenz, J., Peacock, M., Stubbs, J., Whybrow, S., Raats, M. (2013) ‘Cognitive and weight-related correlates of flexible and rigid restrained eating behaviour’, Eating Behaviors, 14(1), pp. 69-72.
4. Timko, C.A., Perone, J. (2005) ‘Rigid and flexible control of eating behavior in a college population’, Eating Behaviors, 6(2), pp. 119-125.
5. Westenhoefer, J., Stunkard, A.J., Pudel, V. (1999) ‘Validation of the flexible and rigid control dimensions of dietary restraint’, International Journal of Eating Disorders, 26(1), pp. 53-64.
6. Conlin, L.A., Aguilar, D.T., Rogers, G.E., Campbell, B.I. (2021) ‘Flexible vs. rigid dieting in resistance-trained individuals seeking to optimize their physiques: A randomized controlled trial’, Journal of the International Society of Sports Nutrition, 18(52).
7. Wing, R.R., Phelan, S. (2005) ‘Long-term weight loss maintenance’, The American Journal of Clinical Nutrition, 82(1), pp. 222-225.
8. Yannakouila, M., Poulimeneas, D., Mamalaki, E., Anastasiou, C.A. (2019) ‘Dietary modifications for weight loss and weight loss maintenance’, Metabolism, 92, pp. 153-162.
9. Meule, A., Westenhöfer, J., Kübler, A. (2011) ‘Food cravings mediate the relationship between rigid, but not flexible control of eating behavior and dieting success’, Appetite, 57(3), pp. 582-584.
10. Timmerman, G.M., Gregg, E.K. (2003) ‘Dieting, Perceived Deprivation, and Preoccupation with Food’, Western Journal of Nursing Research, 25(4), pp. 405-418.
11.  Stewart, T.M., Williamson, D.A., White, M.A. (2002) ‘Rigid vs. flexible dieting: association with eating disorder symptoms in nonobese women’, Appetite, 38(1), pp. 39-44.
12. Culbert, K.M., Racine, S.E., Klump, K.L. (2015) ‘Research Review: What we have learned about the causes of eating disorders – a synthesis of sociocultural, psychological, and biological research’, Journal of Child Psychology and Psychiatry, 56(11), pp. 1141-1164.