In one trial, free breakfasts and dinners arrived on schedule every week for a year and a half. From month six, the scale started climbing anyway. The weight didn't wait for the deliveries to stop.
And the cheapest kind of meal plan, the one you could print tonight, is the one version none of this research put to the test.
The closest thing to a meal box in this research is an 18-month trial from 1993, run by Jeffery's team. Everyone in its weight-loss groups met to learn the same skills, and some groups also got five free breakfasts and five free dinners a week, with a written plan and recipes to go with them.
At the one-year weigh-in, the groups with the food had lost about twice as much: 9.1 kg against 4.5 in the same programme without it. By month 18 the gap had narrowed, 6.4 against 4.1.
That trial doesn't stand alone. A review of 23 trials looked at programmes built around meal replacements, most often shakes, soups and bars, which people were advised to use and in some trials were given. They came out ahead at the one-year mark in every comparison the review made.
One trial inside that review breaks the pattern. Its women got vouchers for ready single-serving main dishes, 14 a week to begin with, cut to 4 a week from the fourth month. They lost weight faster at first, until the lead slipped away: by month six the trial could no longer tell the groups apart.
The first-year answer is real, with an asterisk. The question you probably came with is about what happens after.
Month six, meals still arriving
Delivery blogs and macro coaches agree on one thing: the weight comes back when the plan ends. They just sell different cures.
Here's where that story gets the calendar wrong. In the 18-month trial the food never stopped. The deliveries ran on schedule from the first week to the last.
The weight started coming back at month six anyway. Between month six and month 18, both sides put back about the same number of kilos, roughly 0.3 kg a month each, going by the group averages, which the trial didn't test against each other. On BMI, a measure of weight for height, the food groups put back slightly more.
Read that with a meal box in mind. The food was still in the kitchen, free, every week, and the scale still turned.
For scale: a 21-day plan, or a six-week one, is over long before that trial's first follow-up weigh-in, at six months.
The portioned-food trial points the same way. Its women regained faster than the other groups while their vouchers kept coming, right through month 12. In both trials, the turn came with food still being supplied.
Nothing in the evidence we gathered compares weight before and after the food stopped. The week a subscription ends is still an open page. On what does go with keeping weight off, a separate review of 49 studies found it tracked habits like weighing yourself, moving more and handling emotional eating, not age, income or weight history.
Still ahead, or back to even?
Whether the head start survives the slide comes down to one thing the trials did differently: what happened to the food.
Where the free meals kept coming for all 18 months, the food groups kept a lead to the end, about half the one-year gap. Where the vouchers were cut back after the first months, the lead was gone by month six.
Those two trials differ in more than the food, since one met in groups and the other gave one-to-one sessions. That makes it a pattern to watch, not a rule.
The review sits on the hopeful side: its authors write that the edge over diet advice alone appears to last up to four years, though their two-year check, built on just two trials, couldn't confirm it.
If you've heard that a meal plan makes you lazy about tracking, the 18-month trial points the other way. The groups given food and a plan filled in more food-diary days, not fewer, and in the last six months they came to nearly two-thirds of the group sessions, against about a quarter for the group with neither food nor cash.
The trial's authors raise their own doubt: the free food may simply have been a reason to keep showing up and doing the homework. No study here put a plan up against counting macros, either.
The plan nobody pulled apart
In the delivery trial, the food never came alone: group meetings, a written plan and ready portions all came with it. The meetings can be ruled out: both sides sat in the same weight-loss groups, so its 4.6 kg gap at one year is food against no food. Whether groups beat one-to-one support is its own question.
The meals and the plan are harder to split. They arrived together with recipes and ready portions, and the trial's authors say themselves that which piece mattered wasn't tested. The review's meal replacements and the portioned food came bundled inside whole programmes too.
Which leaves the version you might actually buy. None of our four studies tested a written plan without the food.
That's the PDF on your phone.
The only data on planning comes from a survey of 40,554 French adults. People who planned their own meals were less likely to have obesity, but a survey taken at one moment can't tell whether planning shaped their weight or their weight shaped their planning. Among the men, the link with being overweight didn't show up at all.
We should say why this matters to us: FitChef makes written meal plans. Among our 40,000-plus members (our own platform data, March 2026), about 28% follow the full plan every day, a reminder that a plan on paper and a plan on the plate are different things. The trial with the big first-year gap never measured how much of its delivered food got eaten, either.
The price question, and who was tested
Then there's the bill, which none of these studies measured. In the 18-month trial the food was free, the review reported nothing on what the products cost, and the portioned-food trial's main dishes came by voucher.
That trial's authors did notice why people drifted off. They linked the regain to people using fewer of the portioned foods, influenced by reports that they cost more and by feeling self-conscious and deprived. Price may shape how long people stick with it, but none of these studies tested what paying does to the result.
Every number here is weight on the scale, not fat or muscle, so none of it lines up with the body-composition results on our personal trainer page. As for who was weighed, the review's trials were mostly women and the portioned-food trial only women, while the 18-month trial was half men and took nobody over 45.
From month six on
Put it all together, the way a friend who read all four studies would tell it.
If someone hands you the food, the evidence points to a genuine head start for the first year. Both the 18-month trial and the 23-trial review found it. It's the firmest part of this answer.
What the food didn't buy was protection from the slide. The question worth asking of any plan or delivery service isn't how fast the first weeks go. It's what happens from month six.
And if what you want is the written plan on its own, you're choosing the one version the evidence hasn't settled, either way. That includes ours.
The 18-month trial also tested one more way to keep people going: paying some groups for the weight they lost, up to $25 a week. The money made no difference the trial could find, with the food or without it.
That was one way of paying people. In a small trial of 57 veterans, people who put their own money on the line lost 14.0 lb in 16 weeks against 3.9 lb with monthly weigh-ins. By seven months the trial could no longer tell them apart.
Another head start with a shelf life.
The food's lead peaked at the one-year weigh-in. Measured against the same group programme without it, the free breakfasts and dinners were worth 2.4 kg at six months, 4.6 kg at a year and 2.3 kg at 18 months, so by the end the lead was back to about its six-month size.
The slide was timed differently too, though only in the averages, with no test between the groups. Between months six and twelve, the groups without the food put back about 3 kg and the food groups about 1. In the next six months it flipped: nearly 3 kg back for the food groups, well under 1 for the others.