Six Months with ChatGPT, Looking Back at My Diet in Numbers—Performance Log for February 2026

“Are you actually keeping it up?”
Over the past six months, whenever I was asked that, I would stumble over my words a little.

I was keeping it up. Every day, calmly and steadily.
The reason I haven't written about it isn't because I was slacking off—it's because the records became so deeply embedded in the “background of my life” that I lost the timing to put them into words.

But now that six months have passed, a “stratum of reflection” has finally accumulated.
Today, I will summarize the diet records I’ve been running with ChatGPT, using the figures as of the end of February 2026.

0. Premise of this record

I started my diet on September 1, 2025.

Six months have passed since then. I haven't changed my methods or done anything dramatic along the way.

The content I’ve kept up with is exactly as I wrote at the end of November.

What changed wasn't the method, but the way I kept it up.
And what supported that way of keeping it up was ChatGPT.

1. Results as of the end of February 2026 (in numbers)

Let’s start with the conclusion. In six months, this is where I am.

• Weight: 82kg (end of August) → 73kg (end of February)
  → -9kg

• Blood pressure: 168/127 (September average) → 143/102 (February average)
  → -25mmHg (as a reference)

• Sleep: 5 hours 45 minutes (September average) → 6 hours 50 minutes (February average)
  → +1 hour 5 minutes

• Waist circumference: 91.5cm (end of November checkup) → 89cm (end of February)
  → -2.5cm

At the end of November (3 months in), I was down 6kg.
In the 3 months since then, I’ve lost another 3kg. In other words, weight loss has continued at a pace of roughly 1kg/month.

Honestly, this pace isn't “flashy.”
But precisely because it isn't flashy, I’ve been able to keep it up.

2. Exercise volume (actual results): Aerobics is the star, walking is the core

Exercise continues to be primarily aerobic.
What I chose is walking.

The breakdown looks something like this.

• Gym treadmill
  incline 15%, speed 6.5km/h for 20–30 minutes every day

• Outdoor walks (often not brisk walking)
  10–30 minutes

Step count was maintained at approximately 12,000 steps/day.
It only dropped slightly in late January due to feeling unwell.

In terms of distance, 12,000 steps equals about 10 km.
When this happens every day, it has a significant presence as part of daily life.

3. The treadmill eliminated 'real-world constraints'

I want to say this loudly:
The treadmill really helped me.

In the city, using actual roads to

• walk at 6.5 km/h

• for over 20 minutes

• while maintaining a heart rate of 120 or higher

• continuously

This is almost impossible. You stop at traffic lights, get stuck behind people, and hills aren't conveniently located. There's also the weather.

But the treadmill makes all of that disappear.
The incline, speed, and time are all constant.
That is why I invested without hesitation in an 'environment where I can continue'.

4. The plateau and the trigger for breaking through

It might look like things were going smoothly, but there was a plateau.
From mid-December to mid-January, my weight didn't change much.

The trigger that helped me break through that plateau was,
ironically, a stomach bug in late January.
During this time, I could only do minimal exercise, yet my weight dropped significantly.

Of course, losing weight due to illness is not recommended.
However, I learned one thing here.

A plateau is not a time when your efforts are wasted.
It is also a time when your body is preparing for the next change.

Once I could think that way, the number of times I blamed myself during a plateau decreased.

5. The reason I started incorporating strength training: My body felt lighter

The initial strategy was simple.

• Bodyweight training was difficult because my body was too heavy

• First, lose weight

• Think about strength training after becoming capable of moving

I made sure not to break this order.

However, from around early February, my body started to feel lighter.
There was no "strange discomfort" left after exercise. The feeling that my legs were about to break had decreased.

So, I added strength training little by little.
Rather than starting out of "motivation," it felt more likemy body gave me permissionto do so.

6. Heart Rate and Calories Burned: Numbers Shape Behavior

Heart rate during walking is a mix of outdoors and treadmill.

• Outdoor walking: about 100-110 bpm

• Treadmill: about 150-160 bpm

On average, the overall graph shows a value somewhere in between.
What is important here is not how it looks, but "reproducibility."

Active energy has averaged 821 kcal/day over the past six months.
Even on days when I don't feel well, the goal is "not to hit zero."

For me, I ran things with these rules.

• Even on tough days, let's try for 650 kcal

• If that's impossible, at least do the minimum exercise required

Don't hit zero.
This was the secret to keeping the habit from breaking.

7. Looking at the weight transition graph, there is a real sense of achievement

Looking at the weight trend graph makes me quietly happy.

In particular, the sudden drop in late January was due to a cold.
After recovering, I started strength training.

Rather than "losing weight all at once,"
the fact that I was "able to maintain it without bouncing back" was more valuable to me.

8. Changes in appearance: Others notice before you do

Honestly, it's hard to notice changes in appearance yourself.

Even when I look in the mirror, I don't really think, "Wow, I've lost weight."
However, people I haven't seen in a while

"Huh? Have you lost weight recently?"

have started saying things like that occasionally.
The reason I don't notice is because I see myself every day.

As for my waist circumference, I learned how to measure it during my health checkup at the end of November, so I measure it myself from time to time.
I definitely feel that it has become slimmer than it was six months ago.

It's the same with suits, but even with casual clothes, they slide down without a belt.
A belt has become essential. This is a subtly happy change.

And one more thing.
The feeling of "my leg muscles are just under too much strain" that I felt when I started has been largely resolved over these past three months.
Even when I exercise, I don't have that uncomfortable feeling that my body is about to break.
I feel like my body has changed to a state where it is "ready to move."

9. ChatGPT's predictions: They were mostly accurate

As I mentioned in my article at the end of October, ChatGPT's predictions were mostly accurate.

Of course, since it's a future prediction, it's not 100%.
But at least for me,

• what I should look at

• what pace is realistic

• what might happen along the way (such as plateaus)

It was a "partner that puts things into words" for me.

I have summarized the analysis method in another article, so please take a look if you are interested.

If there is demand, I am also considering sharing the prompts and GPTs.

10. Future Goals: Aiming for All Green

In the health checkup at the end of November, although I managed to get out of the "requires medical examination" (red card) status, it was not all green.

According to ChatGPT's predictions, it is expected to approach normal values around May I plan to take just a blood test around May to check my progress.

By then, not only my triglycerides and cholesterol, but also my weight (BMI) should be within the standard range.
My goal is to escape the metabolic syndrome diagnosis.

Conclusion: What I want to protect most is the version of myself that can keep going

Dieting is, after all, a daily repetition.
Incredibly dull consistency is harder than amazing results.

That is why I don't think I will do anything flashy from here on out.
I will move the numbers little by little while protecting the "version of myself that can keep going."

If you are currently in a plateau or a night where you want to quit.
Let me ask you just one thing.

What you want to fix most right now is it your weight? Or is it the way you keep going?

▼ I am documenting my records in the magazine below.

For first-time readers: