Weight Loss

Intermittent Fasting and OMAD: What Actually Happens When You Stop Eating on a Schedule

One meal a day sounds extreme. Sometimes it is. Here’s when IF works and when it’s just expensive suffering.

AI generated image by the author

The internet will tell you that intermittent fasting is either the greatest weight loss breakthrough since caloric science or a dangerous starvation gimmick being pushed by tech bros who haven’t eaten since Thursday. Neither is accurate. The truth lives somewhere in the middle, which is annoying, but that’s where most truth tends to live.

Here’s what’s worth understanding before you skip breakfast or eat one meal a day and call it a lifestyle.

What We’re Actually Talking About

Intermittent fasting (IF) isn’t a diet. It doesn’t tell you what to eat. It tells you when. The most common version is 16:8 — you eat within an eight-hour window, skip food for sixteen. Some people compress that to 18:6. Others do alternate day fasting. And then there’s OMAD, which stands for One Meal a Day, and is exactly what it sounds like: one meal. Every day. That’s it.

OMAD is the extreme end of the IF spectrum. It’s not a quirky variant. The fasting window is typically 23 hours. You eat for one hour. Some people thrive on it. Some people are absolutely miserable and just don’t admit it.

Why It Works When It Works

The mechanism isn’t magic, and anyone selling it as such is selling you something. The most obvious reason IF helps with weight loss is simple: most people eat less when they have fewer hours available to eat. Shrink the window, shrink the calories. That’s it. No metabolic wizardry required.

But there’s more to it than just cutting eating time. When you haven’t eaten for 12 or more hours, your insulin levels drop significantly. Low insulin tells your body it’s allowed to access stored fat for energy. That’s the part that gets oversimplified into influencer content. The reality is your body is already doing this to some extent every night while you sleep. Fasting just extends that window.

There’s also some evidence that fasting improves insulin sensitivity over time, which matters a lot for people over 60. As we age, insulin resistance becomes increasingly common, and it’s one of the quieter drivers of fat accumulation around the midsection. If fasting helps blunt that resistance even modestly, the downstream effects on body composition are real.

A 2020 review in the New England Journal of Medicine noted that intermittent fasting can produce weight loss, reduce blood pressure, and improve metabolic markers including insulin sensitivity and cholesterol levels. The researchers were careful to say the improvements were often comparable to what you’d get from continuous calorie restriction. Not better, in many cases. Just different.

That word “different” matters. For some people, not counting calories, not weighing food, and just watching the clock is psychologically much easier than traditional dieting. And ease of execution is not a small thing. If you can’t stick to a plan for more than three weeks, it doesn’t matter how elegant the science behind it is.

The Muscle Problem

Here’s where I need to slow down, because this part gets glossed over constantly.

If you’re over 60 and your priority is maintaining or building muscle mass — which it absolutely should be, because muscle is the single best investment you can make in your long-term independence — then OMAD carries real risk.

Muscle protein synthesis, the process by which your body actually builds and repairs muscle tissue, requires adequate protein at regular intervals. Research on leucine thresholds suggests that your body needs somewhere around 2.5 to 3 grams of leucine per meal to maximally trigger muscle building. That’s roughly 30 to 40 grams of quality protein per sitting. If you’re eating one meal a day, you’d have to cram a staggering amount of protein into that single window to hit your daily targets and distribute that leucine stimulus effectively.

The problem is your body doesn’t store excess protein for later use the way it does fat. Once you’ve hit the ceiling of what can be used in a given sitting, the rest gets oxidized or converted. It doesn’t bank it for tomorrow’s muscle repair.

If you’re sedentary and purely focused on fat loss and don’t care about muscle, OMAD might work fine. But if you’re training, especially resistance training, compressing all your nutrition into one hour and hoping your muscles don’t notice is wishful thinking.

Standard 16:8 IF doesn’t carry this problem to the same degree. Two or three meals in an eight-hour window is enough to distribute protein intake and hit those leucine thresholds multiple times. That’s why most coaches who work with older adults and have actually thought this through are more comfortable with 16:8 than OMAD.

The Sustainability Question

This is the one that matters most, and it’s the one that gets the least honest treatment.

The research on long-term adherence to fasting protocols is thin. Most studies run 12 to 24 weeks. That’s not long-term. That’s a semester. Life happens over years and decades, not semesters.

What we do know from observational data and clinical experience is that people who stick with IF tend to do so because it fits their life, not because it’s superior. They’re not breakfast people. They naturally delay eating. They work in environments where skipping lunch isn’t socially awkward. The protocol matched the person.

People who fail at IF usually fail because they’re fighting biology and schedule simultaneously. They’re hungry in the morning and suffering. They’re eating dinner at 5 PM and staring at the wall by 8. They end up so ravenous at the end of the eating window that they overcorrect and eat more than they would have otherwise, which eliminates the caloric benefit entirely.

OMAD has even steeper dropout rates in longer observations, and for obvious reasons. Eating once a day is socially isolating. Most human cultures center around shared meals. Thanksgiving is not improved by watching your family eat while you wait for your one-hour window.

What Older Adults Should Know Specifically

A few things worth flagging for anyone on the back half of 60:

Your hunger signals are less reliable than they were at 35. Older adults often undereat without realizing it, and fasting protocols can compound that. Protein in particular tends to get shortchanged. If you’re going to try IF, track your protein intentionally for at least a month before trusting your appetite to guide you.

Medications change the equation. If you’re taking anything that requires food — metformin, some blood pressure medications, anything with GI side effects — eating once a day or compressing your window dramatically can cause real problems. Talk to your doctor before you start, not after you’ve been dizzy for a week.

Sleep matters too. If you’re doing OMAD and eating your one meal in the evening, you may be going to bed with a full gut and disrupting sleep quality. And sleep quality at our age is not a thing to casually trade away for a fasting protocol. The metabolic and hormonal consequences of poor sleep for older adults are well-documented and genuinely nasty.

The Bottom Line

Intermittent fasting is a legitimate tool. It works for fat loss primarily because it helps people eat less without obsessing over every gram. For some people, especially those who aren’t hungry in the morning and do well with structure, it can be both effective and sustainable. The metabolic benefits beyond caloric reduction are real but modest for most people.

OMAD is a different animal. It’s extreme, it’s hard to sustain, and it’s poorly suited for anyone serious about preserving muscle mass. The people who make it work long-term tend to have lifestyles that accommodate it. They’re not fighting their schedule and their hunger simultaneously.

Neither approach is a key to anything. There are no keys. Weight loss and body composition improvement happen through a consistent caloric deficit, adequate protein, resistance training, and enough sleep to support recovery. IF can be one structure that helps you achieve that. It’s not the only one. It’s not even the best one for most people.

If it fits your life and you can sustain it, use it. If you’re miserable by noon and fantasizing about toast, it doesn’t fit your life. Find something that does.

Stay strong. Stay skeptical.

John Harris, The Proud Boomer