Marine collagen for weight loss: what people who actually took it say

Updated on 12 November 2026 with 41 reviews from people who took British Supplements’ Clean Genuine Hydrolyzed Marine Collagen, written between June 2020 and September 2026, and 3 studies published between 2018 and 2023.

Four months into a bovine collagen, one Mumsnet member had lovely skin but tighter clothes, and wanted to know if anyone else had put weight on. Others came to collagen trying to shift a few pounds, or with loose skin left behind after a big loss. Whether marine collagen helps with weight loss or puts weight on, the people who took it wrote about both.

We went through every review of British Supplements’ Clean Genuine Hydrolyzed Marine Collagen. Of those, 41 mention weight, written between June 2020 and September 2026 by people in the UK. Loose skin after losing weight comes up most, and three wrote that they lost weight while taking it.

If marine collagen itself is new to you, start with what marine collagen is and where it comes from.

Here’s what the 41 reviews that mention weight talk about:

Does collagen help you lose weight?

Yes, collagen helped three people lose weight, according to their reviews of British Supplements’ Clean Genuine Hydrolyzed Marine Collagen. Another 11 took it for their skin, hair or nails while they were losing weight or after. It’s a small group in the reviews. Here’s what one of them wrote:

Does collagen suppress appetite? It eased the hunger pangs for David I.:

What does the research say about collagen and weight loss?

Collagen brought body fat down 1.2kg over 12 weeks, while it rose 0.3kg on placebo. That’s according to a 12-week trial of fish collagen from skate skin, published in Marine Drugs in March 2019, in 90 overweight adults who didn’t change how they ate or moved.

The trial was run at Pusan National University Hospital in Korea, in adults aged 20 to 60, most of them women. It measured body fat with a low-dose X-ray body scan at the start, at six weeks and at 12 weeks, and the gap between the groups first showed at six weeks.

Body weight itself barely moved: up 0.2kg on collagen and 0.7kg on placebo, a difference the researchers didn’t count as real.

Does collagen cause weight gain?

No, collagen didn’t cause weight gain for 40 of the 41 people whose reviews of British Supplements’ Clean Genuine Hydrolyzed Marine Collagen mention weight. The other one gained a few pounds but didn’t look any bigger for it, and nobody wrote that it made them puffy or that they held on to water weight.

Does collagen cause bloating and weight gain?

No, collagen didn’t cause bloating and weight gain together for any of the 41 people who mention weight. Across every review of British Supplements’ Clean Genuine Hydrolyzed Marine Collagen, 10 people wrote about bloating, wind or an upset stomach, and 21 wrote the opposite.

What does the research say about collagen and weight gain?

There was no real difference in weight gain between collagen and placebo: 0.2kg against 0.7kg over 12 weeks. That’s according to the Marine Drugs trial. BMI rose 0.3 on placebo and 0.1 on collagen, and body fat as a share of body weight dropped 0.6 percentage points on collagen and 0.2 on placebo.

Does collagen help with loose skin?

Yes, collagen helped with loose skin after losing weight, according to Peter M., who lost a lot of weight very quickly and whose loose skin around the waist had all tightened after about three months.

Seven people who took British Supplements’ Clean Genuine Hydrolyzed Marine Collagen wrote about loose or saggy skin after losing weight, and one more wrote that it made no difference to their skin. Firmer skin in general is on the page about collagen for skin. Here’s what they wrote:

What does the research say about collagen and loose skin?

Collagen raised two of three skin elasticity measures above placebo by 12 weeks, and skin hydration from six weeks. That’s according to a 12-week trial of fish collagen peptides published in Nutrients in June 2018, in 64 women aged 40 to 60.

Is collagen safe to take for weight loss?

Whether collagen is safe for you to take for weight loss depends on what your GP or a pharmacist says. None of the 41 people whose reviews of British Supplements’ Clean Genuine Hydrolyzed Marine Collagen mention weight wrote about a side effect. Across every review of the product, 41 people wrote that they had no side effects and 28 wrote about one.

If you’re fasting or cutting out carbs, so was L.B., who took British Supplements’ Clean Genuine Hydrolyzed Marine Collagen while fasting and eating keto and lost a lot of weight. Here’s what L.B. wrote:

If you’re losing a lot of weight, so were five of the 11 who took British Supplements’ Clean Genuine Hydrolyzed Marine Collagen for their skin, hair or nails. Here’s what Colin B. wrote:

What does the research say about safety?

The research found no real difference in side effects between collagen peptides and a placebo. That’s according to a review of four placebo-controlled trials in 507 people, published in the Journal of Orthopaedic Surgery and Research in September 2023.

In the Marine Drugs trial, the one complaint, an upset stomach in one person, wasn’t linked to the collagen, and liver, kidney and blood sugar tests showed no change that mattered over its 12 weeks.

Ask your GP or a pharmacist about what to avoid while taking marine collagen if you:

• take anything for your weight, or any other medication
• are pregnant or breastfeeding
• have an operation booked
• have a liver or kidney condition
• have had an eating disorder

Anyone with a fish allergy should not take it.

The pack adds three lines of its own: not to be taken by under 18s, do not exceed the recommended daily dosage, and keep out of reach of children.

Which collagen is best for weight loss?

The best collagen for weight loss is the one with reviews from people who actually took it while they were losing weight. That’s people with names and dates, not what’s printed on the pack. Here’s what three of them who took British Supplements’ Clean Genuine Hydrolyzed Marine Collagen wrote:

FAQ

Does collagen help you lose belly fat?

Collagen didn’t help people lose belly fat in the Marine Drugs trial: the depth of people’s bellies lying down dropped about 0.1cm in both the collagen and placebo groups over 12 weeks. Nobody among the 41 people whose reviews of British Supplements’ Clean Genuine Hydrolyzed Marine Collagen mention weight wrote about belly fat.

Why have I gained weight after taking collagen?

Gaining weight after taking collagen came up for one of the 41 people whose reviews of British Supplements’ Clean Genuine Hydrolyzed Marine Collagen mention weight, who gained a few pounds while taking it and looked no fatter, and nobody else wrote that they’d gained. In the Marine Drugs trial, the placebo group gained a little more weight than the collagen group did.

Does collagen help with menopause weight gain?

Nobody wrote that collagen helped with menopause weight gain, so the reviews don’t answer it either way. Of the 149 people who wrote about the menopause in their reviews of British Supplements’ Clean Genuine Hydrolyzed Marine Collagen, one wrote about their weight, the same person who gained a few pounds, and nobody wrote about a menopause belly. What they did write about is on the page about collagen for menopause.