- Theory: Hunger mechanisms
- Application: Recommendations
Reading time: 23 min. (Audio version here)
Managing hunger is the key to a successful diet and becoming incredibly lean.
Let me repeat that. THE KEY.
Appetite control is not a sexy topic, and often overlooked. At its core, it is the only thing standing between you and your nutritional targets. Getting a handle on hunger will close the gap between your target intake and your actual intake – evermore necessary in today’s obesogenic environment.
Walk into any newsagent, and you will notice that they have handpicked the cheapest, most calorie dense and hyperpalatable foods, all displayed in nice colourful packaging. How kind of them.
The obesity crisis is a complex function of environmental, genetic, socioeconomic and psychological predispositions – all of which ultimately disrupt satiety cues – causing individuals to eat a calorie excess.
Hunger is an unconscious drive. Willpower and gritting your teeth can only take you so far. We aren’t samurais.
Otherwise telling people to ’eat less, move more’ would have solved the obesity crisis years ago. Instead, our appetite buttons are being pushed, shifting the balance towards overeating and weight gain.
Forced underfeeding causes a cascade of physiological responses, such as depressed basal metabolic rate (BMR), increased appetite, and reduced non exercise activity thermogenesis (NEAT), causing a return to the original, if not a higher, bodyweight. In the US, 40% of Americans are dieting at any given time, yet 68.8% are overweight or obese.
Food producers have worked hard to short-circuit our satiety mechanisms to keep us fat and hungry:
“100 years ago the average person needed to exert an incredible amount of effort to reach 300 lbs, but now that food science and the drug industry have mastered the correct signaling process for unlimited fat mass, we longer need to pay a nickel to see the fat man or woman at the carnival. Sit in front of Walmart and watch as 300-plus pounders stream by in herds.” – Kiefer
We already have the odds stacked against us. Factor in that if you’re reading this, you’re looking to get silly-lean, where the hunger demons really start to creep out. We need a little more than the typical weightwatchers ‘eat from a smaller plate’ advice.
This article is the ultimate guide to stacking the odds back in your favour, quashing hunger and drifting into single digit bodyfat.
As much as the fitness industry loves to polarise and offer a binary cause for everything (e.g. ‘carbs are the devil’, ‘insulin causes fat gain’, etc. etc.), appetite control is unfortunately pretty complex.
There are a number of overlapping mechanisms, which influence hunger and satiety. I have categorised these as follows:
– Mechanical factors
– Hormonal factors
– Food choices and quirks
– Behavioural factors
2.1 Mechanical factors
Gastric mechanoreceptors (stretch receptors) respond hormonally to the physical volume of food in your gut by inducing sharper ghrelin suppression, increased rate of fat metabolism, and making you subjectively feel fuller for longer. Higher volume food substitutions are confirmed to aid long-term weight loss in subjects.
‘Ingested food evokes satiety in the GI tract primarily by two effects, i.e. by mechanical stimulation and by the release of peptides through the chemical effects of food (Cummings and Overduin 2007). However, pure mechanical stimulation, such as gastric distention, is insufficient to terminate ingestion, but contributes to satiety when acting in concert with pregastric and postgastric stimuli (Ritter 2004) … many of the intestinal peptides also inhibit gastric emptying, thus enhancing gastric mechanoreceptor stimulation, too.”
Food volume is closely related to sensory cues for the calorie density of food, known as the cephalic phase. This phase responds to the taste, smell and texture of food and has a surprisingly significant effect on gastric hormone secretion and satiety.
A study on nasogastric feeding (straight into the stomach, bypassing the mouth entirely) found the following:
“Increasing the energy content of infused food, but not the volume, did not affect satiety. Thus, when sensory cues were bypassed, the volume of liquid food infused intragastrically affected subsequent energy intake in both lean and obese women. These results suggest that gastric and postgastric mechanisms are involved in the effects of high-volume, low-energy-dense foods on satiety.”
Hopefully don’t intubate yourself to hit your macros, but liquid meals bypass chewing, entering the GI tract with minimal oro-sensory exposure. The physiological effects of the cephalic phase are minimised, reducing the satiety response. Necking that 800kcal mega-frappe-latte-deluxe-with-cream-to-go will set you up to eat more in the rest of the day, compared to eating an 800kcal spaghetti bolognese.
The combination of volume and sensory factors make liquid meals a very poor choice for maximising satiety.
The take home point:
A) Isocaloric substitutions with higher volume —> Lower intake
e.g. Substituting 40g jelly beans (38g carbohydrates) for 223g boiled potato (38g carbohydrates) = greater satiety
B) Isovolumetric substitution with greater calorie density —> Increased intake
e.g. 500ml skimmed milk vs 500ml whole milk
2.2 Hormonal factors
A huge number of hormones and neurotransmitters have indirect effects on appetite. The main hormones directly involved in appetite control are:
– Peptide YY (PYY)
– Neuropeptide Y (NPY)
These interact in the following ways:
Simple right? Bear in mind all of the factors overlap – volume, composition, and even the smell of foods produce hormonal effects that work in conjunction to induce satiety. Here is where I start to realise I bit off more than I could chew writing this article (I’m so funny sometimes).
2.2.1 The fed state
The satiety hormone leptin is released from fat cells. The more dieted you are, the lower your circulating leptin, stimulating appetite and a reduction in BMR. Ghrelin responds to metabolic signals, triggering hunger to maintain energy homeostasis. Dieting to low levels of bodyfat generally elevate ghrelin and suppress leptin:
The body resists losing weight by compensating with appetite and BMR, which is further dysregulated by the food manufacturers, making dieting an uphill struggle. Particularly in the final stages into single digit bodyfat, extreme hormonal changes form metabolic, adherence and mood obstacles (see 2.5).
2.2.2 Sleep deprivation:
Sleep deprivation is a chronic stressor, with a negative effect on appetite control, stimulating ghrelin, increasing blood glucose and causing a transient insulin resistance. The elevated cortisol and cascade of effects worsen impulse control, cravings and dietary restraint, setting you up for overeating and metabolic syndromes in the long term.
Sleep duration plays a pivotal role hunger regulation: it is positively associated with circulating leptin independent of BMI, and inversely associated with circulating ghrelin. Meta analyses show BMI is generally 0.35 points lower for every additional hour of sleep.
This is covered in depth here, where the main conclusion is that exercise has a variable effect on appetite in both direction and magnitude, confounded by:
– Unconscious slippage of intake vs tracking
– Training style and intensity
– Effects of post-exercise compensatory energy expenditure.
It follows that homeostatic forces will maximise energy efficiency and resist exercise-induced weight loss, amounting to ∼30% of exercise-induced deficit. These compensatory mechanisms appear heterogenous and are likely interdependent on other appetite factors. All we can conclude is that exercise produces a mixed response, based on the individual.
In terms of our recommendations, we are not masochists or crossfitters at PropaneFitness. Our goal is for you to lose fat and gain muscle with the minimum effective dose of input: Occam’s razor. Your training volume and cardio should already be the minimum necessary to maintain progression – i.e. further reduction would compromise your progress and is not a variable we can play with. If you personally find that extra cardio does suppress your appetite, adding this in is an option, but factor in your limited recovery capacity.
2.2.4 Diurnal variation: To breakfast, or not to breakfast?
Ghrelin and cortisol reach a peak in the morning, in line with hunger.
Berkhan offers an interesting theory as to why a high carbohydrate breakfast makes us hungry:
The point is that the circadian cortisol peak coincides with breakfast, and that this is the only point during the day that cortisol reaches high enough levels to exert an acute and pronounced effect on feeding-induced insulin secretion. What I mean here is that, at the cortisol awakening response peak, cortisol climbs high enough to agonize glucocorticoid receptors.
This changes the non-genomic interaction between cortisol and insulin action from being permissively restraining by the former, as seen at other times during the day due to mineralocorticoid binding dominance, to a non-genomic stimulating, or synergistic if you will, effect (Vila et al., 2010; Dallman et al., 1995) Short-term exposure to cortisol powerfully augments insulin secretion and this is the key point here.
Tread carefully. Theorising diurnal hormone variations and macronutrient interactions is potentially a rabbit hole. For our purposes, it is simpler to look at the evidence around effects of meal frequency, timing and compositions on satiety ratings and intake. For example, if you are eating breakfast, a protein-dominant breakfast appears to reduce subsequent intake compared with a carbohydrate one.
2.2.5 Meal frequency
Regularity is a more critical factor than a specific meal cadence for hunger control. Appetite generally compensates for meal frequency outside of the extremes, meaning hunger control is worse with 2 or fewer meals, or more than 6 meals per day. A safe option would be 3 meals/day for satiety and muscle preservation . Intermittent fasting may be helpful if it fits your schedule, particularly if your fast is during a time where you’re not idle and thinking about food. Anecdotally, we find intermittent fasting can have a dark side, which can be avoided when periodised. I’m sure that it goes without saying by now that ‘stoking the metabolic fire’ is a myth, and meal frequency within a normal range has little impact on BMR.
Artificial sweeteners and zero calorie foods are a lifesaver during a diet. Human studies reject the idea that artificial sweeteners spike insulin or cause weight gain. This fear is likely “a good example to explain the term “reverse causation” [fat people buy diet products vs. diet products make lean people fat]”. A few studies actually found an improvement in satiety and body composition and reduction in food intake in contrast to sucrose-sweetened drinks, which increased calorie intake in some cases. Potential mechanisms for this are still uncertain but may be related to GLP-1 promotion.
Habitual diet soda drinkers displayed augmented responses in reward pathways on fMRI readings – both in response to sucrose and sweetened drinks. The fMRI response for sucrose vs. sweetener was identical with habitual diet-soda drinkers compared to the habitual sugar soda drinkers. This indicates the potential for non-nutritive sweeteners to rewire neural reward centres, which is interesting in the context of their association with reduced calorie intake.
2.3 Food properties and quirks
Key contents and physical properties of foods affect satiety:
– Energy density and volume – covered above
– Glycaemic index
– Flavour & perception of indulgence
Unfortunately, the evidence on the satiety value of individual macros is murky with no clear frontrunners and is of little relevance here unless you’re a weirdo and eat single-macro meals. Fibre and protein do appear to have stronger effects on satiety, but with no established dose-response relationship. This likely won’t come as news to you, and if you’re on the Propane Protocol, you’ll be getting enough of both.
Alcohol, needs a brief mention as the honorary macronutrient. Metabolism of alcohol results in an excess of NADH:
Excess NADH in the cytosol favours conversion of gluconeogenic precursors pyruvate and oxaloacetate away from glucose and towards lactate & malate. The diversion away from gluconeogenesis can result in hypoglycaemia and alcohol-induced munchies, associated with drunken donner kebab consumption.
2.3.2 Glycaemic index
Interestingly, there’s no clear relationship between glycaemic index and satiety. A better guide is the satiety index, covered in 2.4.
2.3.3 Flavour & texture
We appear to have flavour and texture specific cravings or specific-satiety: It’s possible to satisfy your sweet/salty craving, and possibly even your hard/soft craving. No sniggering please.
There’s a psychological benefit to flexible dieting and being able to indulge in ’naughty’ foods during your diet, both to satisfy cravings and to feel like a normal human being. . However, there is a potential for overuse of sweet and salty foods to overstimulate the orosensory receptors, disrupt reward pathways and form addictive behaviours. Particularly so with hyperpalatable foods and MSG, which increase intake in subjects. Salt also reduces the satiety response to fat and could pave the way to obesity. Once you pop, you can’t stop.
Texture is also a factor in how satiating or palatable a food is. Compare highly viscous, melt-in-your-mouth buttery steak or chocolate to celery – which would you rather more of?
White bread is porous, so is degraded more easily in the GI tract than pasta, although organic acids and common additives, such as sodium propionate lengthen gastric emptying time, increasing satiety value. This, along with the normal-human-being argument are possible reasons that white bread is positively associated with dietary adherence.
It’s likely that dairy, grain and other foods have their quirks and individual effects on the gut, responsible for their satiating powers.
This explains a couple of things. While getting obese eating nutrient-dense foods can be done, it’s pretty tough. The irony of today’s fast-food industry is that foods are often extremely calorie dense yet nutrient scarce. Certain boxes of satiety are ticked, but the underlying undernourishment causes appetite to remain dysregulated. Mineral or vitamin deficiencies continue to push the ‘eat more’ buttons in an attempt to restore the balance. But many will hear this signal from the body as ‘eat more [chocolate] buttons’ instead.
2.4 Satiety index
Now that we’re thoroughly confused by all the different factors affecting satiety, how do we determine which foods are more filling? Luckily, Holt has done the work for us and collated an index as a reference of 38 foods in 240kcal portions, based on participants’ fullness ratings at regular intervals and subsequent intake. This neatly accounts for rate of gastric emptying and fullness over time. If the satiety index is <100, the satiety effect of the food is less than that of white wheat bread, if it is >100, the food is more satiating then white bread.
Holt’s research concluded the following:
“There were significant differences in satiety both within and between the six food categories. The highest SI score was produced by boiled potatoes (323 +/- 51%) which was seven-fold higher than the lowest SI score of the croissant (47 +/- 17%). Most foods (76%) had an SI score greater than or equal to white bread.
The amount of energy eaten immediately after 120 min correlated negatively with the mean satiety AUC responses (r = -0.37, P < 0.05, n = 43) thereby supporting the subjective satiety ratings. SI scores correlated positively with the serving weight of the foods (r = 0.66, P < 0.001, n = 38) and negatively with palatability ratings (r = -0.64, P < 0.001, n = 38).
Protein, fibre, and water contents of the test foods correlated positively with SI scores (r = 0.37, P < 0.05, n = 38; r = 0.46, P < 0.01; and r = 0.64, P < 0.001; respectively) whereas fat content was negatively associated (r = -0.43, P < 0.01).
CONCLUSION: The results show that isoenergetic servings of different foods differ greatly in their satiating capacities.”
An interesting observation: the potato absolutely BOSSED it at 323, but crisps = 91. Same food, different satiety value due to water, texture, palatability, and added oil, making it a fat-dominant food rather than a carb-dominant one. This is why nutritional dogma, demonising certain foods must be taken with a pinch of salt, and why glycaemic index doesn’t cut it. Eating 1000kcal of boiled potato vs 1000kcal of crisps: one is practically a challenge, the other you could accidentally inhale watching a movie.
2.5 Behavioural & emotional factors
2.5.1 Boredom & convenience
Eating out of boredom stems from procrastination and idle hands rather than a physiological desire to eat. If you’re working an office job where the biscuits are always within reach, the mind naturally drifts towards food in dull moments.
2.5.2 Stress & trauma
The bigger threat to appetite control, however, is emotionally fuelled eating.
“Stress consistently increased intake of hyperpalatable foods specifically… even in the absence of hunger and lack of homeostatic need for calories’.
Repeated and uncontrollable stress can over time dysregulate the HPA [hypothalamic pituitary adrenal] axis, which consequently affects energy homeostasis and eating behavior.
Chronic activation of the HPA axis can alter glucose metabolism, promote insulin resistance and influence multiple appetite-related hormones and hypothalamic neuropeptides.
Moreover, those under chronic stress tend to eat more under acute stress conditions and show heighted preference for and consumption of hyperpalatable, energy-dense foods high in sugar and fat.
These foods can exploit the potential for addiction in those already vulnerable.
“Uncontrollable stress changes eating patterns and the salience and consumption of hyperpalatable foods; over time, this could lead to neurobiological adaptations that promote increasingly compulsive behavior. The stressed brain expresses both a strong drive to eat and an impaired capacity to inhibit eating – together creating a potent formula for obesity”.
The effects of stress on behavioural control and impulsivity make us susceptible to substance abuse in general. Cheap, convenient foods are a perfect default option for short term relief. The typical cycle:
stress —> impaired restraint —> impulsive eating —> self flagellation —> attempt to ameliorate negative state —> emotional/comfort eating.
Eating under stress:
” When I was fat and unhappy, the only moments of respite I got were when I was eating. Now mealtimes are sometimes lame, because that’s the way it can be when you’re eating healthily. But all the time between meals, I feel great.” Feel great all the time, rather than just at meal times.” – Chris Pratt
With self-focused emotional eating, food becomes solace from discomfort. However, it adopts a different role when an individually is consciously dieting. Those exercising dietary restraint tended to lapse into higher food intake under stress. In this case, food is raised to a pedestal as the forbidden fruit, with a greater propensity for binges.
“It is hypothesized that people actively trying to restrain food intake may deplete the cognitive resources necessary to deal with stressors, thereby impairing their inhibitory control which in turn increases the likelihood of overeating. Lack of control over life events may lead to desperate and ineffective attempts to control eating such as by deprivation from a particular food followed by later binging.”
Emotions are complex, and we all have our vulnerabilities. The key point is that they have concrete, measurable effects on our neurochemistry, propensity for addiction, impulse control, and ability to stay lean. It is not an insignificant factor in a successful diet. This website is predominantly read by men, who are notoriously shit at seeking professional help for emotional distress. Some form of emotional processing and stress management is critical when dieting to low levels of bodyfat: ask any precontest bodybuilder. They’re mentally and physically depleted, marshalling all of their cognitive resources towards dietary restraint.
Hopefully it’s all coming together now that appetite is really a multi-headed monster with overlapping causes. A multi-pronged approach is required to tame it.
For a meal with a given macronutrient target, make substitutions to bump up the volume.
Fortunately, you won’t make your stomach baggy or get desensitised to the effect from abusing the high volume foods.
Use the satiety index as your guide. Some personal favourites:
While drinking more during a meal does not appear to reduce total daily intake, preparing food with more water does. e.g. rice prepared with more water. Pick foods with higher water content, and cook with more water to increase the satiety value.
3.3 Food choices
Bearing flavour-specific satiety in mind and opt for lower calorie foods that satisfy those criteria, e.g. anchovies or pickle for savoury cravings.
As for sweet cravings, I’m not convinced by the fMRI evidence that normal use of artificial sweeteners would be counter productive, and much of the other evidence supports their effectiveness. Moderate use of sugar-free foods and diet sodas would be good options to manage cravings. Additionally, try keeping some dark chocolate in your cupboard for sweet cravings: subjects ate 17% less pizza after eating 100g dark chocolate compared to milk chocolate.
Dairy foods have a decent satiety track record. Milk amplifies the post-prandial ghrelin decline, and low fat yoghurt and whey have been shown to reduce subsequent total daily intake by 100-200kcal
Recommendation: Include more dairy products into your diet, and drink half a scoop of whey before each meal. We use MP True Whey: wide variety of flavours and good quality control.
Additionally, start the day with a creamy banana and peanut butter protein latte to take advantage of the satiating effects of a high protein breakfast.
A variety of available food increases ad libitum intake by up to a third.
The diversity of stimulation may eventually develop tolerance to the reward pathways:
‘healthy adults placed under a nutritionally adequate but monotonous diet, compared to those on an unrestricted diet, showed greater activation of the hippocampus, insula, and caudate in response to cues of foods they favored. Repeated stimulation of the reward pathways through hyperpalatable food may lead to neurobiological adaptations that eventually increase the compulsive nature of overeating characterized by the frequent drive to initiate eating’
This mechanism is not exclusive to food.
Interestingly, a milk-only diet produced weight loss over 16 weeks comparable to the most successful drug treatment in obese participants. The researchers’ conclusion was that a novel but simple diet was the reason for its success. Perhaps milk as the choice of drink was also a contributor.
Recommendation: Variety and palatability are inversely associated with satiety, so reduce the variety of foods and take things back to blandness. Reset your tolerance and you’ll be able to enjoy treats more, with less compulsion.
3.4 Meal frequency
– Avoid the extremes: stick to 3-5 meals per day at convenient times for you.
– Experiment with meal size and macro composition using high satiety index foods to determine the minimum calories you need to suppress hunger sufficiently for 3-5 hours.
– Spread protein evenly with a slight skew towards the meal with the highest calories. Anecdotally, many find backloading their carbs to be helpful.
– Develop a rhythm and eat your meals at roughly the same time each day.
– Intermittent fasting: ONLY IF the fasting period helps you stay productive and keep your mind off food. Do not fast if you spend the fasting period fantasising about your next meal. The goal is to reduce the percentage of the day that you think about food.
– Plan meals that fit your schedule. This is why we aren’t prescriptive with meal times – it’s meaningless without knowing your personal timetable.
See our full guide to becoming a sleep warrior.
1. Control your sleep environment (dark, cool, quiet), use neurochill, limit caffeine and follow the sleeptocol
2. You need to spend at least 7 hours and 20 minutes with your eyes closed, head on the pillow. More if time allows
3. Make yourself a morning routine list and make it so that a monkey could follow it. Become as efficient as possible with your morning tasks so you get as much sleep as possible.
– Cultivate self-compassion, give yourself a break when you need to. Stress will derail your diet.
– Strive to detach your self image from your diet & training. Training is something you do, not something you are.
– Meditate. There’s more on meditation in the free Propane Protocol 10 week course , but bear in mind meditation is a discipline. Pop-spirituality and the blogosphere write to sell. Quick-fix platitudes and easily digestible (hyperpalatable, you could say) ideas are more profitable than diligent patience. So calibrate your expectations – 10 minutes per day isn’t sufficient to access and heal the deeper reaches of your mind, just as 10 minute per day in the gym is unlikely to be enough to make decent progress. You’ll get out what you put in.
Supplements should not be the first port of call. Make changes further down the pyramid first.
3.7.1 Appetite suppressants
Some compounds are quite effective for appetite suppression. Even some legal ones. As a rule of thumb, the potential for side effects and risk is proportional to the strength of the appetite suppression. Amphetamine related, centrally acting drugs often used for appetite suppression, leading to a minefield of psychiatric and cardiovascular risks in pursuit of leanness. The downside is that when you’re in a deficit, catecholamines are already high. As Eric Helms pointed out at his 2013 seminar, yohimbine is used to experimentally induce panic attacks. So including sympathetic agonists at a time where you’re most neurotic and highly strung isn’t the brightest idea.
Our recommendation is simply to avoid on a cost-benefit basis.
Other effective suppressants include 5-HTP, producing notable appetite and weight reduction, or chromium, which has weaker effects. Green tea should theoretically reduce appetite, which is in line with our experience.
It also looks like PINE NUTS may also be helpful as they increase CCK secretion.
3.7.2 Appetite stimulants:
Some commonly used appetite stimulants:
– Lime squeezed in water
– Supplemental digestive enzymes
Ghrelin mimetics or inramuscular vitamin B12 may be prescribed for severe, clinically low appetite.
Hopefully this post has provided some food for thought. A final checklist to improve appetite control:
– Use the satiety index as your guide
– Reduce variety
– Don’t abuse extreme flavours
– Do abuse high volume foods
– Increase dairy intake, try half a scoop of whey before each meal
– Improve your sleep environment and aim for 7.5 hours
– Eat around 3 meals per day at regular times
– Intermittent fasting if it suits your schedule
– Stay distracted between meals, get out of the kitchen, minimise food preparation time
– Practice self care & stress management
But hey, it’s just advice – these recommendations are starting points based on the evidence, with aim to push the odds back in your favour. There’s room for experimentation: if you feel fuller eating 6 meals per day, carb frontloading, carb backloading, go for it.
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10 replies on “The ultimate hunger & satiety guide: The KEY to getting lean”
Superb article, congratulation guys on this, well structured and simple to understand.
On dieting for getting lean what’s your opinion on “refeed days”? when? why? on that day just do a simple “all you can eat” refeed or base your refeed in carbs?
Thanks Fall – glad you enjoyed it. Short answer: Base refeeds on calories and carbs, although long answer may need a post of its own!
Great work gents,
Addressing a highly complex area in a clear and engaging manner. Alway’s enjoy reading your blogs.
Keep it up!
Thanks Alex – glad to hear it :)
Oh man, this is amazing! Thank you :)
What does the lime-y water pre-meal do, exactly?
Thanks Shane :) – Lime: just aiding with stomach pH and digestion, nothing fancy
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