Mechanism

How it works

The lipotropic agents in Lipo-C work synergistically to facilitate hepatic fat metabolism: methionine donates methyl groups for phosphatidylcholine synthesis, choline prevents hepatic steatosis by enabling VLDL export of triglycerides, and inositol modulates insulin signaling to improve glucose and lipid homeostasis. L-carnitine shuttles long-chain fatty acids across the inner mitochondrial membrane for beta-oxidation, directly increasing the rate of fat burning. B vitamins (B1, B2, B6, B12) serve as essential cofactors in energy metabolism pathways including the citric acid cycle and fatty acid oxidation.

Reported in research

Benefits

Supports mobilization and breakdown of fat deposits, including visceral and hepatic fat
Enhances mitochondrial fatty acid oxidation via L-carnitine activity
Promotes liver health by reducing lipid accumulation and supporting detoxification pathways
Boosts energy levels through improved metabolic efficiency and B vitamin cofactor activity

Context, not a prescription

Dosing

Typical range: 1 ml injection (containing standard blend concentrations) 1-3x per week (Subcutaneous, Intramuscular)
Cycle length: 4-12 weeks
Half-life: Varies by component: B12 ~6 days (serum), carnitine ~15 hours, choline ~12-24 hours

Safety

Side effects & contraindications

Possible side effects

Injection site redness, swelling, or mild pain
Nausea or GI upset (particularly with higher doses of choline or methionine)
Fishy body odor due to choline/methionine metabolism
Headache or dizziness, especially early in use
Rare: allergic reaction at injection site

Contraindications

Known allergy or hypersensitivity to any component of the blend (B vitamins, choline, carnitine, methionine, inositol)
Active liver disease or severe hepatic impairment
Pregnancy or breastfeeding (due to unestablished safety profile of injectable blend)
Trimethylaminuria (fish-odor syndrome) — choline and methionine metabolism may worsen symptoms
Concurrent use of anticoagulants without medical supervision (B12 may interact)

Research information, not medical advice. Always consult a licensed clinician before considering any peptide.

In depth

Full profile

What it does

Gradual reduction in body fat (especially when dieting), improved energy levels, reduced fatigue, and sometimes improved mood.

How it works

Think of your liver as a busy shipping warehouse. Fat is the cargo that needs to be packaged and sent out. Lipo-C is like hiring extra workers (choline, methionine), better forklifts (carnitine), and upgrading the electrical system (B vitamins) so the warehouse can process and ship fat much faster instead of letting it pile up.

When injected, the ingredients are quickly absorbed into the bloodstream. They travel to the liver and muscles, where they ramp up fat processing, reduce fat buildup in the liver, and help convert fat into energy. B vitamins also support nerve function and red blood cell production, which can contribute to improved energy and mood.

What to expect

Some people notice increased energy within the first few days due to B12. Fat loss changes typically become noticeable after 2–4 weeks when combined with a caloric deficit and exercise.

Week 1: Energy boost (particularly from B12) is often the first noticeable change. Injection site may be slightly sore. Fat loss changes are not yet visible.
Weeks 2-4: Metabolic effects begin to compound; some users report reduced appetite and improved energy. Mild fat loss may become noticeable when combined with diet and exercise.
Weeks 4-12: Consistent users typically report cumulative fat loss, better energy, and improved workout recovery. Liver markers may improve if hepatic fat was elevated.

Good to know

Always inject with sterile technique to avoid infection
Start with 1 injection per week to assess tolerance before increasing frequency
Pair with a balanced diet and regular exercise for meaningful fat-loss results

Staying safe

Mild soreness or redness at the injection site
Slight nausea, especially if injected on an empty stomach
A fishy or sulfur-like body odor (from choline and methionine breakdown)

Avoid if you have:

People with known allergies to B vitamins, choline, or any blend component
Pregnant or breastfeeding individuals
Anyone with a diagnosed liver disease without medical supervision

Overview

Reductions in hepatic triglyceride content (measurable by MRI or liver biopsy in clinical settings), improvements in lipid panel (particularly triglycerides), enhanced fatty acid oxidation rates measured by indirect calorimetry, improved insulin sensitivity indices, and potential improvements in plasma homocysteine if B12/B6 were previously deficient.

How it works

Consider the liver as a highly regulated lipid processing plant governed by rate-limiting enzymatic bottlenecks. Choline and methionine act as substrate-level regulators that remove the rate-limiting constraint on VLDL packaging (the 'loading dock throughput'), while carnitine resolves the mitochondrial 'import bottleneck' for fatty acid substrates destined for beta-oxidation. Inositol acts as an upstream signal transducer recalibrating insulin receptor sensitivity — effectively tuning the plant's control system. B vitamins are the essential cofactors that keep every enzymatic assembly line operating at peak efficiency.

Following IM or subcutaneous administration, the components achieve peak plasma concentrations within 30–60 minutes. L-Carnitine plasma levels plateau and are actively transported into skeletal muscle and cardiac tissue via OCTN2 transporters. Choline is incorporated into phosphatidylcholine or oxidized to betaine (which re-enters the methionine cycle). Cyanocobalamin is converted to methylcobalamin and adenosylcobalamin intracellularly. Methionine enters the SAM cycle, donating methyl groups and generating homocysteine (which must be remethylated by B12/folate-dependent methionine synthase — emphasizing the interdependence of blend components).

Onset & timeline

B12 effects on energy and erythropoiesis: days to 1–2 weeks. Hepatic lipid metabolism improvements (reflected in ALT/AST or imaging): 4–8 weeks of consistent use. Carnitine muscle carnitine stores require 2–4 weeks of supplementation to saturate. Inositol-mediated insulin sensitization may take 4–8 weeks.

Days 1-3: Rapid absorption of B12 restores tissue stores if deficient; carnitine begins accumulating in plasma. Minimal acute metabolic shift detectable.
Weeks 1-2: Hepatic phosphatidylcholine synthesis increases with adequate choline substrate; early improvements in VLDL export may begin. Muscle carnitine pools start to saturate with repeated dosing. Insulin signaling improvements via inositol begin accumulating.
Weeks 2-8: Sustained improvements in hepatic lipid handling, potential reductions in serum triglycerides, and enhanced skeletal muscle fatty acid oxidation. With dietary compliance, measurable reductions in body fat percentage and possible normalization of mildly elevated liver enzymes in fatty liver presentations.

Getting the most from it

Ensure adequate folate co-administration to support homocysteine remethylation when using methionine-containing blends
Rotate injection sites to minimize lipodystrophy and sterile abscess risk
Monitor liver function tests (ALT, AST, GGT) every 4–6 weeks if using high-frequency dosing protocols
For patients with MTHFR C677T polymorphisms, consider methylated B12 (methylcobalamin) over cyanocobalamin

Common side effects

Trimethylaminuria-like odor from TMAO production via gut microbiome metabolism of choline and methionine — particularly in individuals with FMO3 enzyme polymorphisms
Transient hyperhomocysteinemia if methionine dosing is excessive relative to B12/folate availability
Injection site reactions: erythema, induration, sterile abscess (rare with proper technique)

Mechanism of action

Lipo-C functions as a multi-target lipotropic agent. Choline is the rate-limiting substrate for phosphatidylcholine synthesis via the CDP-choline (Kennedy) pathway; adequate phosphatidylcholine is essential for VLDL assembly and hepatic triglyceride export, preventing non-alcoholic fatty liver disease (NAFLD). Methionine provides labile methyl groups via the methionine cycle, supporting SAM-dependent methylation reactions including phosphatidylcholine biosynthesis via PEMT. Inositol acts as a second messenger precursor (IP3 via phospholipase C), modulating insulin receptor signaling and reducing hepatic insulin resistance. L-Carnitine facilitates the obligate transport of long-chain acyl-CoA moieties across the inner mitochondrial membrane via the carnitine-acylcarnitine translocase system, enabling beta-oxidation; carnitine also buffers the acyl-CoA/CoASH ratio, reducing acyl-CoA-mediated inhibition of pyruvate dehydrogenase. B vitamins serve as cofactors: thiamine (B1) for pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase; riboflavin (B2) as FAD in electron transport; pyridoxine (B6) for transamination reactions; cyanocobalamin (B12) for methionine synthase and methylmalonyl-CoA mutase.

Following IM or subcutaneous administration, the components achieve peak plasma concentrations within 30–60 minutes. L-Carnitine plasma levels plateau and are actively transported into skeletal muscle and cardiac tissue via OCTN2 transporters. Choline is incorporated into phosphatidylcholine or oxidized to betaine (which re-enters the methionine cycle). Cyanocobalamin is converted to methylcobalamin and adenosylcobalamin intracellularly. Methionine enters the SAM cycle, donating methyl groups and generating homocysteine (which must be remethylated by B12/folate-dependent methionine synthase — emphasizing the interdependence of blend components).

Pharmacodynamics

B12 effects on energy and erythropoiesis: days to 1–2 weeks. Hepatic lipid metabolism improvements (reflected in ALT/AST or imaging): 4–8 weeks of consistent use. Carnitine muscle carnitine stores require 2–4 weeks of supplementation to saturate. Inositol-mediated insulin sensitization may take 4–8 weeks.

Reductions in hepatic triglyceride content (measurable by MRI or liver biopsy in clinical settings), improvements in lipid panel (particularly triglycerides), enhanced fatty acid oxidation rates measured by indirect calorimetry, improved insulin sensitivity indices, and potential improvements in plasma homocysteine if B12/B6 were previously deficient.

Timeline

Days 1-3: Rapid absorption of B12 restores tissue stores if deficient; carnitine begins accumulating in plasma. Minimal acute metabolic shift detectable.
Weeks 1-2: Hepatic phosphatidylcholine synthesis increases with adequate choline substrate; early improvements in VLDL export may begin. Muscle carnitine pools start to saturate with repeated dosing. Insulin signaling improvements via inositol begin accumulating.
Weeks 2-8: Sustained improvements in hepatic lipid handling, potential reductions in serum triglycerides, and enhanced skeletal muscle fatty acid oxidation. With dietary compliance, measurable reductions in body fat percentage and possible normalization of mildly elevated liver enzymes in fatty liver presentations.

Comparisons

Lipo-C Injectable Blend — effectiveness Moderate, safety Good, cost $$, Medium to use
AOD-9604 (fat-loss peptide) — effectiveness Moderate, safety Good, cost $$$, Medium to use

Adverse effects

Common:

Trimethylaminuria-like odor from TMAO production via gut microbiome metabolism of choline and methionine — particularly in individuals with FMO3 enzyme polymorphisms
Transient hyperhomocysteinemia if methionine dosing is excessive relative to B12/folate availability
Injection site reactions: erythema, induration, sterile abscess (rare with proper technique)

Rare:

Anaphylaxis to cyanocobalamin (estimated incidence <1 in 10,000 injections) — cyanide ligand occasionally implicated; hydroxocobalamin is preferred in sensitive individuals
Paradoxical hepatotoxicity with supraphysiological methionine dosing due to SAM/SAH imbalance and oxidative stress — primarily a theoretical concern at standard compounded doses

Contraindications & risk mitigation

Contraindicated in:

Patients with trimethylaminuria (FMO3 deficiency) — choline and methionine dramatically worsen symptoms
Patients with homocystinuria or severe MTHFR mutations without folate co-supplementation
Patients on Leber's hereditary optic neuropathy (LHON) — cyanocobalamin may be contraindicated; hydroxocobalamin preferred
Active or chronic hepatocellular disease where methionine clearance is impaired

Ensure adequate folate co-administration to support homocysteine remethylation when using methionine-containing blends
Rotate injection sites to minimize lipodystrophy and sterile abscess risk
Monitor liver function tests (ALT, AST, GGT) every 4–6 weeks if using high-frequency dosing protocols
For patients with MTHFR C677T polymorphisms, consider methylated B12 (methylcobalamin) over cyanocobalamin

Qué hace

Gradual reduction in body fat (especially when dieting), improved energy levels, reduced fatigue, and sometimes improved mood.

Cómo funciona

Think of your liver as a busy shipping warehouse. Fat is the cargo that needs to be packaged and sent out. Lipo-C is like hiring extra workers (choline, methionine), better forklifts (carnitine), and upgrading the electrical system (B vitamins) so the warehouse can process and ship fat much faster instead of letting it pile up.

When injected, the ingredients are quickly absorbed into the bloodstream. They travel to the liver and muscles, where they ramp up fat processing, reduce fat buildup in the liver, and help convert fat into energy. B vitamins also support nerve function and red blood cell production, which can contribute to improved energy and mood.

Qué esperar

Some people notice increased energy within the first few days due to B12. Fat loss changes typically become noticeable after 2–4 weeks when combined with a caloric deficit and exercise.

Week 1: Energy boost (particularly from B12) is often the first noticeable change. Injection site may be slightly sore. Fat loss changes are not yet visible.
Weeks 2-4: Metabolic effects begin to compound; some users report reduced appetite and improved energy. Mild fat loss may become noticeable when combined with diet and exercise.
Weeks 4-12: Consistent users typically report cumulative fat loss, better energy, and improved workout recovery. Liver markers may improve if hepatic fat was elevated.

Bueno saber

Always inject with sterile technique to avoid infection
Start with 1 injection per week to assess tolerance before increasing frequency
Pair with a balanced diet and regular exercise for meaningful fat-loss results

Manteniéndose seguro

Mild soreness or redness at the injection site
Slight nausea, especially if injected on an empty stomach
A fishy or sulfur-like body odor (from choline and methionine breakdown)

Evitar si tienes:

People with known allergies to B vitamins, choline, or any blend component
Pregnant or breastfeeding individuals
Anyone with a diagnosed liver disease without medical supervision

Descripción general

Reductions in hepatic triglyceride content (measurable by MRI or liver biopsy in clinical settings), improvements in lipid panel (particularly triglycerides), enhanced fatty acid oxidation rates measured by indirect calorimetry, improved insulin sensitivity indices, and potential improvements in plasma homocysteine if B12/B6 were previously deficient.

Cómo funciona

Consider the liver as a highly regulated lipid processing plant governed by rate-limiting enzymatic bottlenecks. Choline and methionine act as substrate-level regulators that remove the rate-limiting constraint on VLDL packaging (the 'loading dock throughput'), while carnitine resolves the mitochondrial 'import bottleneck' for fatty acid substrates destined for beta-oxidation. Inositol acts as an upstream signal transducer recalibrating insulin receptor sensitivity — effectively tuning the plant's control system. B vitamins are the essential cofactors that keep every enzymatic assembly line operating at peak efficiency.

Following IM or subcutaneous administration, the components achieve peak plasma concentrations within 30–60 minutes. L-Carnitine plasma levels plateau and are actively transported into skeletal muscle and cardiac tissue via OCTN2 transporters. Choline is incorporated into phosphatidylcholine or oxidized to betaine (which re-enters the methionine cycle). Cyanocobalamin is converted to methylcobalamin and adenosylcobalamin intracellularly. Methionine enters the SAM cycle, donating methyl groups and generating homocysteine (which must be remethylated by B12/folate-dependent methionine synthase — emphasizing the interdependence of blend components).

Inicio y cronología

B12 effects on energy and erythropoiesis: days to 1–2 weeks. Hepatic lipid metabolism improvements (reflected in ALT/AST or imaging): 4–8 weeks of consistent use. Carnitine muscle carnitine stores require 2–4 weeks of supplementation to saturate. Inositol-mediated insulin sensitization may take 4–8 weeks.

Days 1-3: Rapid absorption of B12 restores tissue stores if deficient; carnitine begins accumulating in plasma. Minimal acute metabolic shift detectable.
Weeks 1-2: Hepatic phosphatidylcholine synthesis increases with adequate choline substrate; early improvements in VLDL export may begin. Muscle carnitine pools start to saturate with repeated dosing. Insulin signaling improvements via inositol begin accumulating.
Weeks 2-8: Sustained improvements in hepatic lipid handling, potential reductions in serum triglycerides, and enhanced skeletal muscle fatty acid oxidation. With dietary compliance, measurable reductions in body fat percentage and possible normalization of mildly elevated liver enzymes in fatty liver presentations.

Cómo aprovecharlo al máximo

Ensure adequate folate co-administration to support homocysteine remethylation when using methionine-containing blends
Rotate injection sites to minimize lipodystrophy and sterile abscess risk
Monitor liver function tests (ALT, AST, GGT) every 4–6 weeks if using high-frequency dosing protocols
For patients with MTHFR C677T polymorphisms, consider methylated B12 (methylcobalamin) over cyanocobalamin

Efectos secundarios comunes

Trimethylaminuria-like odor from TMAO production via gut microbiome metabolism of choline and methionine — particularly in individuals with FMO3 enzyme polymorphisms
Transient hyperhomocysteinemia if methionine dosing is excessive relative to B12/folate availability
Injection site reactions: erythema, induration, sterile abscess (rare with proper technique)

Mecanismo de acción

Lipo-C functions as a multi-target lipotropic agent. Choline is the rate-limiting substrate for phosphatidylcholine synthesis via the CDP-choline (Kennedy) pathway; adequate phosphatidylcholine is essential for VLDL assembly and hepatic triglyceride export, preventing non-alcoholic fatty liver disease (NAFLD). Methionine provides labile methyl groups via the methionine cycle, supporting SAM-dependent methylation reactions including phosphatidylcholine biosynthesis via PEMT. Inositol acts as a second messenger precursor (IP3 via phospholipase C), modulating insulin receptor signaling and reducing hepatic insulin resistance. L-Carnitine facilitates the obligate transport of long-chain acyl-CoA moieties across the inner mitochondrial membrane via the carnitine-acylcarnitine translocase system, enabling beta-oxidation; carnitine also buffers the acyl-CoA/CoASH ratio, reducing acyl-CoA-mediated inhibition of pyruvate dehydrogenase. B vitamins serve as cofactors: thiamine (B1) for pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase; riboflavin (B2) as FAD in electron transport; pyridoxine (B6) for transamination reactions; cyanocobalamin (B12) for methionine synthase and methylmalonyl-CoA mutase.

Following IM or subcutaneous administration, the components achieve peak plasma concentrations within 30–60 minutes. L-Carnitine plasma levels plateau and are actively transported into skeletal muscle and cardiac tissue via OCTN2 transporters. Choline is incorporated into phosphatidylcholine or oxidized to betaine (which re-enters the methionine cycle). Cyanocobalamin is converted to methylcobalamin and adenosylcobalamin intracellularly. Methionine enters the SAM cycle, donating methyl groups and generating homocysteine (which must be remethylated by B12/folate-dependent methionine synthase — emphasizing the interdependence of blend components).

Farmacodinamia

B12 effects on energy and erythropoiesis: days to 1–2 weeks. Hepatic lipid metabolism improvements (reflected in ALT/AST or imaging): 4–8 weeks of consistent use. Carnitine muscle carnitine stores require 2–4 weeks of supplementation to saturate. Inositol-mediated insulin sensitization may take 4–8 weeks.

Reductions in hepatic triglyceride content (measurable by MRI or liver biopsy in clinical settings), improvements in lipid panel (particularly triglycerides), enhanced fatty acid oxidation rates measured by indirect calorimetry, improved insulin sensitivity indices, and potential improvements in plasma homocysteine if B12/B6 were previously deficient.

Cronología

Days 1-3: Rapid absorption of B12 restores tissue stores if deficient; carnitine begins accumulating in plasma. Minimal acute metabolic shift detectable.
Weeks 1-2: Hepatic phosphatidylcholine synthesis increases with adequate choline substrate; early improvements in VLDL export may begin. Muscle carnitine pools start to saturate with repeated dosing. Insulin signaling improvements via inositol begin accumulating.
Weeks 2-8: Sustained improvements in hepatic lipid handling, potential reductions in serum triglycerides, and enhanced skeletal muscle fatty acid oxidation. With dietary compliance, measurable reductions in body fat percentage and possible normalization of mildly elevated liver enzymes in fatty liver presentations.

Comparaciones

Lipo-C Injectable Blend — efectividad Moderate, seguridad Good, costo $$, Medium de usar
AOD-9604 (fat-loss peptide) — efectividad Moderate, seguridad Good, costo $$$, Medium de usar

Efectos adversos

Comunes:

Trimethylaminuria-like odor from TMAO production via gut microbiome metabolism of choline and methionine — particularly in individuals with FMO3 enzyme polymorphisms
Transient hyperhomocysteinemia if methionine dosing is excessive relative to B12/folate availability
Injection site reactions: erythema, induration, sterile abscess (rare with proper technique)

Raros:

Anaphylaxis to cyanocobalamin (estimated incidence <1 in 10,000 injections) — cyanide ligand occasionally implicated; hydroxocobalamin is preferred in sensitive individuals
Paradoxical hepatotoxicity with supraphysiological methionine dosing due to SAM/SAH imbalance and oxidative stress — primarily a theoretical concern at standard compounded doses

Contraindicaciones y mitigación de riesgos

Contraindicado en:

Patients with trimethylaminuria (FMO3 deficiency) — choline and methionine dramatically worsen symptoms
Patients with homocystinuria or severe MTHFR mutations without folate co-supplementation
Patients on Leber's hereditary optic neuropathy (LHON) — cyanocobalamin may be contraindicated; hydroxocobalamin preferred
Active or chronic hepatocellular disease where methionine clearance is impaired

Ensure adequate folate co-administration to support homocysteine remethylation when using methionine-containing blends
Rotate injection sites to minimize lipodystrophy and sterile abscess risk
Monitor liver function tests (ALT, AST, GGT) every 4–6 weeks if using high-frequency dosing protocols
For patients with MTHFR C677T polymorphisms, consider methylated B12 (methylcobalamin) over cyanocobalamin

Reference data

Specifications

Molecular formula: Blend (no single formula); key components: Choline C5H13NO, L-Methionine C5H11NO2S, Inositol C6H12O6, L-Carnitine C7H15NO3, Cyanocobalamin C63H88CoN14O14P
Molecular weight: Blend — component weights range from ~149 Da (methionine) to ~1355 Da (cyanocobalamin)
Half-life: Varies by component: B12 ~6 days (serum), carnitine ~15 hours, choline ~12-24 hours
Route: Subcutaneous, Intramuscular
Cycle length: 4-12 weeks
Storage: Refrigerate at 2–8°C (36–46°F); protect from light; do not freeze. Use within the period indicated by the compounding pharmacy, typically 30–90 days. Discard if solution appears cloudy or discolored.
Legal status: Not FDA-approved as a drug; individual components are legally available as supplements or compounded preparations. Compounded injectable blends require a prescription in the US and must be prepared by a licensed compounding pharmacy.

FAQ

Common questions

Is there clinical evidence for injectable lipotropic blends specifically?

Direct RCT evidence for the specific Lipo-C combination as an injectable blend is limited. However, individual components have robust mechanistic and clinical evidence: oral L-carnitine supplementation has demonstrated fat loss and metabolic benefits in meta-analyses (Pooyandjoo et al., 2016, Obesity Reviews); choline deficiency is a recognized cause of NAFLD in human feeding studies; inositol has clinical evidence in PCOS and metabolic syndrome (Nordio & Proietti, 2012). The injectable route provides superior bioavailability compared to oral administration, particularly for carnitine which has ~15% oral bioavailability vs. near-complete parenteral bioavailability.

How does Lipo-C compare to GLP-1 agonists for fat loss?

GLP-1 agonists (semaglutide, tirzepatide) demonstrate substantially greater magnitude of fat loss in clinical trials (15-22% body weight reduction) via central appetite suppression and peripheral metabolic effects. Lipo-C operates through distinct peripheral metabolic mechanisms and produces far more modest fat loss effects. They can theoretically be complementary — Lipo-C addressing hepatic lipid clearance and mitochondrial substrate utilization while GLP-1 agonists suppress intake — but direct combination studies are absent.

What is the evidence level?

This compound is classified as Limited human data. Some human data exists but trials are small, short-term, or not yet replicated.

Research

Research & sources

Limited human

Current evidence for Lipo-C is rated as Limited human data. Limited human data is available.

1. The effect of L-carnitine supplementation on obesity: a systematic review and meta-analysis of randomized controlled trials (2016) — Obesity Reviews, Pooyandjoo M et al., doi:10.1111/obr.12436
2. Choline: An Essential Nutrient for Public Health (2009) — Nutrition Reviews, Zeisel SH & da Costa KA, doi:10.1111/j.1753-4887.2009.00246.x
3. Inositol and metabolic syndrome: mechanisms and clinical applications (2012) — International Journal of Endocrinology, Nordio M & Proietti E
4. Methionine metabolism in health and cancer: a nexus of diet and precision medicine (2021) — Nature Reviews Cancer, Sanderson SM et al., doi:10.1038/s41568-021-00375-3

Explore

Often discussed alongside

Semaglutide · fat-loss AOD-9604 · fat-loss CJC-1295 · growth Ipamorelin · growth Tesamorelin · fat-loss