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Why Diets Fail and “Eat Less, Move More” is Bad Advice

by Menno Henselmans
Home/Blog/Protect Your Mental Wellbeing During the COVID-19 Pandemic

It’s safe to say obesity is a problem. Over 2 out of 3 people in the US are overweight and over 1 in 3 is obese. Even with help, most people don’t lose more than a few percent bodyweight after years of dieting and the majority of people gain back most of the weight they lost (yo-yo effect).

My clients routinely lose this amount of fat in a matter of weeks. Moreover, they achieve not only large, but also lasting body composition change.

I mainly coach bodybuilders, and bodybuilders are not very well-liked. I understand why: in the media all you see is unnaturally muscular, tanned men and women lined up in what seems to be some sort of muscle worship fetish. Yet in spite of their poor reputation, this stigmatized subculture does know the cure to obesity.

Basically, bodybuilders achieve what everyone on a diet wants: to lose fat, not muscle. That’s why I essentially treat all my clients that want to lose fat like I would treat a bodybuilder. Bodybuilding is just the more successful version of ‘dieting’.

But who am I kidding? You already know how to lose fat, right? Who cares about bodybuilders? Everyone knows: “Eat less, move more.” Dead wrong. This piece of advice is single handedly responsible for more failed diets than McDonald’s. Here’s why.

Why Diets Fail

Mother Nature gifted us with a supreme ruler that tells us when to eat and how much to eat: the sensation of hunger. Like other feelings, hunger gives us purpose and direction. Hunger motivates us to eat something like fear motivates us to avoid something.

Research has found that not being hungry is the most important predictor of successful weight loss. Not monitoring your diet, not self-restraint, not seeking help. Hunger is the enemy. Hunger makes you eat more than intended. Without hunger, dieting would be as easy as just consciously deciding to eat less.

Hunger is a formidable adversary, because evolution made our hunger regulation homeostatic in nature: the leaner you get, the hungrier you become. That’s great if you need to get off your butt to go forage or hunt so you don’t starve. Not so much when you’re having a stare-down with an extra large pizza in the supermarket.

Decision Fatigue

There’s a second piece of the puzzle of why diets fail. Hunger is uncomfortable, but why do we give in to it against our better judgment?

It’s the same reason we procrastinate on our studies, don’t go to bed on time and make impulsive decisions. Some psychologists call it ego depletion. Somewhat like a muscle, the brain becomes fatigued after exertion. We have a limited capacity for higher-level decision-making, which includes decisions involving math, logical reasoning and complex tasks requiring rational thought or planning. We suffer from decision fatigue.

Self-control is one of these complex decisions. Self-control requires us to consciously decide to override our primitive urge to eat. This kind ofself-control is a limited ability.

Humans are relatively good at this compared to other animals, but we are not robots. When our cognitive ability has fatigued, our primitive instincts guide our actions, and we’ll basically eat whatever’s available until we’re satiated.

Hunger plus decision fatigue equals diet failure

This is why most diets fail in the evening. After a long, stressful day at work, you come home hungry and your brain is too foggy to think about what to cook. You open your fridge and a pack of ready-to-eat microwave wraps looks you right in the eye. Decision fatigue has set in and you don’t have the cognitive resources anymore to resist your hunger. Therefore, you opt for convenience foods instead of diet foods.

The Cost-Benefit of Moving More

Common advice is to take the stairs instead of the elevator. Or park your car further away from work or your house so you have to walk a bit. The benefit is self-evident, right? Actually, it’s not, and neither is the cost.

These small benefits do not weigh up against the hidden cost: decision fatigue from fatiguing your brain every time see a staircase or you have to park your car. Constantly thinking about ways to increase your activity level requires effortful self-control. Combine this with a stressful day at work and you’ve got the recipe for a cheat meal. A single cheat meal can undo weeks or even a month of ‘moving more’.

As a long term strategy, ‘moving more’ is even worse. As you lose weight, your body becomes more conservative with energy and motivates you to lower your activity level by making you lazier.

Bodybuilders realize this. Here’s a photo from the Arnold Classic, a major fitness conference. It went viral in fitness circles under headlines as ‘bodybuilders not fit enough to take the stairs’. No, bodybuilders just know that taking those stairs is a needless effort. Conserving mental energy is far more important than expending physical energy. Bodybuilders instead invest their energy in structured exercise.

‘Move More’ vs. Structured Exercise

None of this in any way implies that exercise is bad for you on a diet. But the crucial feature of successful exercise is structure.

Structure is the key to lifestyle change. You need to plan in advance so that you avoid having to make dozens of daily decisions about diet and physical activity. Investing in a structured exercise program frees your mind from decision fatigue. As the saying goes, “Failing to plan is planning to fail.”

Why Cardio is Overrated

So what kind of structured exercise should you do? High intensity exercise like weight training is best. High intensity exercise spares muscle mass on a diet. If you don’t engage in sufficiently heavy exercise when losing weight, you will likely lose muscle mass. You may think you don’t care about muscle mass, but the more muscle mass you lose, the more your metabolism slows down. So the less you have to eat.

I did no cardio whatsoever – just weight training – to get in condition for the photo shoot below. Almost none of my clients, including competitive physique athletes, do cardio.

Menno Henselmans

Building muscle mass increases metabolism. Researchers have compared natural bodybuilders to a control group with the same fat percentage and height. The bodybuilders had a 14% higher resting metabolic rate. When both groups were inactive all day, the bodybuilders burned 354 more calories because of their increased level of muscle mass. That means the bodybuilders burned more calories by sitting on their butts than the inactive subjects did when walking 4 miles (6.4 km) a day.

And by no means do you have to become hugely muscular to benefit from this. Elderly people can increase their resting energy expenditure by 8% in just 16 weeks of weight training.

A recent 12-year study of 10,500 Average Joes found that in the long run, weight training was over twice as effective as vigorous aerobics at getting a slimmer waist.

The short-term benefit of burning a few extra calories with cardio does not weigh up against the long-term benefits of increasing your metabolism with high-intensity exercise.

Don’t like weight training? No problem. Explosive sports like rowing, tennis, martial arts, korfball and volleyball are also considered high-intensity. Long-term sustainability in your lifestyle is more important than what kind of exercise you choose.

Eat More, Not Less

So neither ‘moving more’ nor forcing yourself to perform exercise you despise is sustainable. Therefore, neither is successful in the long-term. The same goes for the diet advice to ‘eat less’.

‘Eating less’ implies sticking to the same food choices but simply eating less of them. This requires constant self-control by constantly eating less than your appetite signals you to. As the diet progresses and you become hungrier, you must eat even less as your metabolism slows down, which is when the struggle becomes exponentially more difficult. It’s no surprise that this is how most diets fail.

The solution? Eat more, not less. In my photo above I was eating close to 9 pounds (~4 kg) of food every day. I just ate low-calorie foods. I mostly ate fruits, vegetables and lean animal protein sources. In fact, it’s rare that I don’t eat at least 4.5 pounds (2 kg) of food in a given day.

Eating more low-calorie foods is the reason paleo diets are so successful at causing fat loss. One study compared overweight men eating a paleo diet to the government-approved Mediterranean diet.The paleo group automatically consumed 24% fewer calories than the Mediterranean group and was just as satiated, even though both groups were eating the same amount of protein and fiber. The paleo group also managed to consume the same amount of nutrients while eating 24% fewer calories.

With a little creativity, you can still eat amazingly delicious foods. I ate a huge slice of this cheesecake every day for example. If you want help with your meal planning, I highly recommend I outsourced my own meal planning this way, and many top personal trainers are doing the same. Whether you eat keto, paleo, vegetarian or low FODMAP, you can eat awesome recipes with minimal cooking.

For example, the typical Mediterranean lunch: 2 large slices of whole-wheat bread with cheese, 1 glass of semi-skimmed milk and an apple. Compare that to these 3 huge Sashimi Omelet Wraps. Both meals contain ~620 calories, but I know which I prefer.

Sashimi Omelet Wrap

If you manage your meal plan carefully, you don’t even need to track your calories. My client Connor made his 8-week transformation without any form of calorie monitoring. I advised him a list of foods to eat and when to eat them. Along with careful lifestyle and appetite management, he ate as much as he wanted.

Connor before and after 8 weeks of coaching by Menno Henselmans


Hunger, failure and weight regain have become the norm in diets. The reason is not lack of willpower or genetics. Unless you have a serious medical condition, there is no reason you can’t get lean and stay lean. Bodybuilders do it all the time. It doesn’t require endless hours of cardio, eating bland food or constant hunger.

Instead, invest your energy in a structured exercise program instead of trivial decisions about your activity level. Most importantly, you must have a good diet strategy to manage decision fatigue and hunger.

Terminator Pose picture licensed under the Creative Commons.


The Paleo movement incorporates several different optimizing perspectives for helping you improve your health, all based on the latest science. Everyone is different. We want to support you in understanding your unique genetic makeup, symptoms and health goals so you can choose the path that is right for you.

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Menno Henselmans

Menno Henselmans is a physique coach, fitness model and scientific author. A former business consultant specialized in advanced statistical data analysis, he traded his company car to do what he’s truly passionate about: help serious trainees attain their ideal physique. His background in science and statistics led to his Bayesian Bodybuilding method.