Hello friend,

Weight loss is commonly thought of as “burning fat.” While true, this is kind of vague and doesn’t really explain the full picture.

For us to understand what is really happening, it helps to think of the body like a chemistry lab mixed with a budgeting problem.

Chemistry explains where the mass goes.
Budgeting explains why it goes there.
Training and food choices decide whether you lose fat, muscle, or both.

So let’s break down exactly what’s going on when you “burn fat.”

Your body weight at any given moment is a combination of:

That last one matters more than people think. It’s common to see day-to-day swings of a couple pounds from water, glycogen, sodium, stress, and digestion alone, even when fat loss is steady.

This is why your first week of dieting often looks amazing and then things stall. Early loss is frequently a lot of glycogen, water, and food volume. Don’t be discouraged, this is normal.

Glycogen is stored with water. When you eat fewer carbs and calories, glycogen stores drop, and the associated water drops with it. That’s why the scale moves quickly at first, even though you did not lose five pounds of fat in four days.

Fat loss is always about burning more calories than you take in. That caloric deficit may come from eating less, exercising more, or a mix of the two.

Your body burns a lot of calories just staying alive. That baseline is your resting metabolism (often called basal metabolic rate or BMR).

Then you spend some energy digesting and processing food, which is the thermic effect of food. Protein is especially “expensive” to process, roughly 20–30% of protein’s calories, versus 5–10% for carbohydrates and 0–3% for fat.

The rest are burned from movement. Movement includes deliberate exercise, but also everything you do that is not exercise, like walking around, standing, fidgeting, or chores. That bucket is called NEAT or non-exercise activity thermogenesis.

Some studies have found NEAT variability of up to 2000 kcal/day between individuals of similar body size, depending on occupation and spontaneous movement. Keep that in mind as you plan your daily caloric intake.

When you eat less than you burn, your body covers the gap by drawing on stored energy and, to some extent, stored tissue.

At a high level, three things happen at once:

You cannot completely avoid losing some lean mass, but you can shift the ratio in your favor by eating extra protein and lifting weights.

A lot of diet frustration comes from using static mental math in a dynamic system.

Caloric intake requirements tend to change as time goes on, because energy expenditure changes as body mass and behavior change.

As you lose weight, you burn fewer calories since you have less mass, and therefore a lower cost to move. But there can also be adaptive effects where energy expenditure drops more than you would predict, a phenomenon called adaptive thermogenesis.

Then there’s appetite.

In one study, people who lost weight showed persistent changes in multiple appetite-related hormones one year later, in a direction that would encourage regain.

That combination of lower caloric burn and higher drive to eat is why maintaining weight loss can feel harder than losing it.

Here’s the strategy I actually use for dieting. It works well for me, but everyone’s situation is a little different, so consider this a framework, not gospel.

Here’s the TLDR:

1. Aim to lose 1-2 lb of body weight per week.

2. Cut 500-1000 kcal below your maintenance calories. Weigh in weekly and adjust if you’re not trending down.

3. Get roughly 1 g or protein per pound of bodyweight daily.

4. Aim for at least 3–5 days per week of resistance training, keeping intensity up. Muscle sticks around when you give your body a reason to keep it.

5. Walk more and add cardio, but don’t sacrifice strength or recovery.

6. Center each meal around protein, keep fiber high, use carbs to fuel tough workouts.

7. Structured breaks can help with adherence. They’re not magic but may make things more sustainable.

8. Don’t crash diet, prioritize sleep, and avoid stacking fatigue from too many hard habits at once.

Okay, now the details.

A moderate deficit is boring and effective.

I aim for 750 kcal/day below maintenance, and over time, that ends up being about 1.5 lbs lost per week. 500 kcal/day would be about 1 lb, and 1000 kcal/day would be about 2 lbs per week. Usually, one of these round numbers is the easiest to stick to. The math is easiest, results are consistent and measurable, and it’s not too difficult.

Any more below maintenance usually means losing a larger proportion of muscle mass during the diet, so I try to avoid it. Plus, it’s much harder.

Make sure you are tracking your weight, at least weekly, so you can adjust calorie intake if needed.

Protein helps in three ways. It supports muscle protein synthesis when calories are low, it increases satiety, and it has a higher thermic effect than carbs or fat, so slightly more of its calories are spent processing it.

I aim for 1 g of protein per pound of bodyweight. I’ve tried higher and lower protein intakes and found them less effective, but your experience may vary. Pick something close to this, give it a try, and adjust if you need to.

Muscle is metabolically expensive tissue. In a deficit, your body will keep what it is forced to keep. Resistance training is the forcing signal.

During a cut, I usually try to keep weights relatively heavy and make sure total training volume stays high. If the weights have to drop as strength fades, add in an extra set or two.

A lot of “metabolism slowing” is really just moving less. NEAT can vary enormously between people and can drift downward during dieting without you noticing.

The simplest, least destructive intervention is often just walking more. It is low fatigue, low injury risk, and it does not usually compete with lifting recovery the way hard cardio can. I like to walk for a few minutes after each workout, just to account for any NEAT decreases.

If you want to do cardio for health or enjoyment, great. Just be careful with recovery. A steep deficit plus high-volume lifting plus lots of intense cardio is how people end up weaker, mentally fried, or injured.

For me, 1-2 days per week of hard cardio is plenty.

The hormonal shifts during and after weight loss can persist and push appetite upward.

That means you want your diet to be structured around foods and patterns that make hunger signals quieter. For me, that means high protein, high carbs, and lower fats. Carbs help more in training for me than fats, but each person will be slightly different here.

Most people find some combination of higher protein, higher fiber, higher food volume, and predictable meals seems to help.

If you only rely on willpower, you are choosing the most failure-prone control system.

Intermittent energy restriction has been studied as a way to improve adherence and potentially attenuate some compensatory responses.

The MATADOR study is a well-known example.

Personally, one cheat day each week where I eat up to maintenance seems to be enough if I’m starting to struggle with diet adherence.

Taking longer structured breaks at maintenance can certainly make a long cut more livable.

If you have a history of disordered eating or significant medical conditions, aggressive dieting can be a big risk. In those cases it’s worth getting professional input before changing things.

Prompt: A titanic world-tortoise (mountain-sized) rises from a black, storm-tossed sea, its shell transformed into a wandering fortress-city of stacked stone terraces, wind-torn banners, and glowing hearths; cascading waterfalls spill from the shell’s rim into the ocean like silver curtains. In the foreground, a small storm-sailed skiff rides a towering wave, crew silhouetted, aiming a grappling line toward a rope-bridge dangling from the tortoise-city. Above, a cyclonic sky splits open with a spiral of auroral lightning forming a radiant halo, casting rim light along wet stone and sea spray; floating bioluminescent jellyfish-like spirits drift through the air near the fortress lanterns. Composition: dramatic low angle from wave level, strong diagonal sweep of the wave leading into the colossal tortoise silhouette, city lights as warm focal points against the cold storm; luminous blue-gold palette with teal shadows and hot amber glows, etched stone texture, wind-whipped cloth, atmospheric depth, mist and spray particles, crisp readable silhouettes. illustrative epic fantasy, strong coarse film grain, painterly texture, canvas tooth, subtle halftone speckle, high-contrast cinematic lighting, volumetric haze, rim light, glowing accents, atmospheric perspective, not photorealistic, no text, no watermark, no UI.

Got a second? Give some feedback on today’s article so we can keep making improvements to The Manifold.

PS—I’m doing a cut right now, and these are the exact ideas I’m using, so hopefully this helps!