As I understand it, losing weight is very simple to understand — and once you change a few habits, simple to implement.
Your body's energy comes from food. The amount of energy in food is measured in calories. Asking "how many calories does this food have?" is the same as asking "how much energy does this food have?"
When your body isn't given enough energy through food, it burns its own fat and muscle instead for energy.
The two outcomes
If every day for 6 months you don't give your body enough energy from food, you will lose fat (and muscle, if you aren't stimulating muscle growth by lifting weights). At the end you'll be able to factually state:
"Over the last 6 months, I ate fewer calories than my body needed."
If every day for 6 months you give your body more energy than it needs, you will gain fat (and muscle, if you are stimulating muscle growth by lifting weights). At the end you'll be able to factually state:
"Over the last 6 months, I ate more calories than my body needed."
The body sees the excess calories and says "Thanks very much, we'll keep that for later!" and stores it as fat — or uses it to build muscle if you're stimulating muscle growth by lifting weights.
An example
The amount of calories each person needs is different depending on age, weight and height. You can use our calculator to work out yours.
A sedentary 42-year-old male who weighs 97kg and is 194cm tall burns about 2,373 calories per day. So:
2,000
Slowly loses weight
Eats less than he burns, so the body pulls the extra energy it needs from stored fat.
2,500
Slowly gains weight
Eats more than he burns, so the body has excess energy it doesn't need and stores it as fat.
His maintenance number is ~2,373 calories/day. Eat under it to lose, over it to gain.
Two things to note
Women's body weight can increase by around 5 lbs in a month depending on the menstrual cycle. In that case, average weight over several months is a better indicator of progress than average weight over one month.
Everyone's weight fluctuates day to day, so take the average over time rather than reading into any single morning on the scale.
Now the hard bit
That was the science. Doing the science in your own home is the hard part, and you have to find what works for you. A company that delivers 3 calorie-controlled meals a day? Cooking your own meals? Bringing a food scale to lunch? Overnight oats? Batch cooking? A mix?
Personally, I find it easier to cook at home almost everything I eat, weigh it before I eat it, then tell an AI how much and of what I'm eating.
I make the home cooking easy by not spending a lot of time on it. I'll batch cook 1kg of chicken with 5 minutes of prep making a simple marinade, cook 3 days of carbs in advance, and keep veggies on hand that I can just add in. Or do a big chili with 1.5kg of beef and veggies and eat that for 3 days across most of my meals.
It's not rocket science. You're either doing it or you're not.
It's not a magic formula based on vibes. If you want to do it, do it. If you don't, don't. Your call.
DM Phil to join the cult